information Hydrologic

\I Hydrologic

information systems

Prepared by

the Panel on Systems for the Acquisition, Transmission and Processing of Hydrological Data

,(SAPHYDATA)

of the Co-ordinating Council of the International

Hydrological Decade Edited by G. W.

WHETSTONE

and V. J. GRIGORIEV

A

Unesco - W M O

Paris Geneva 1972

Studies and reports in hydrology 14

11. World water balance: Proceedings of the Reading symposium, July 1970 / Bilan hydrique mondial: Actes du colloque de Reading, juillet 1970. Vols. 1-3. (Co-edition IASH-Unesco / CoCdition AIHS-Unesco.)

12*. Research on representative and experimental basins: Proceedings of the Wellington (N. X.) symposium, December 1970 / Recherches sur les bassins reprisentatifs et exptimentaux:

Actes du colloque de Wellington (N.X.), dkcembre 1970.

13*. Hydrometry: Proceedings of the Koblenz symposium, September 1970 / Hydrome'trie: Actes du colloque de Koblenz, septembre 1970. (Co-edition IAHS-Unesco-WMO / Co-edition AIHS- Unesco-OMM.)

Hydrologic information systems. (Co-edition Unesco-WMO.) 14.

* To be published. For details of the complete series please see the list printed at the end of this work.

Published jointly by the

United Nations Educational, Scientific and Cultural Organization

Place de Fontenoy, 75 Pa1is-7~

and the

World Meteorological Organization 41 Avenue Giuseppe Motta, Geneva Printed by Imprimeries Populaires, Geneva LC NO. 72-90686

The

publication do not imply the expression of any opinion whatsoever on the part of the publishers concerning the legal status of any country or territory, or of its authorities, or concerning the frontiers of any country or territory.

1972 International Book Year

0 Unesco

-

Printed in Switzerland SC.72/XX.l2/A

Preface

The International Hydrological Decade (IHD) 1965-74 was launched by the thirteenth session of the General Conference of Unesco to promote international co-operation in research and studies and the training of specialists and technicians in scientific hydrology.

Its purpose is to enable all countries to make a fuller assessment of their water resources and a more rational use of them as man’s demands for water constantly increase in face of developments in population, industry and agriculture. In 1971 National Committees for the Decade had been formed in 107 of Unesco’s 125 Member States to carry out national activities and to contribute to regional and international activities within the programme of the Decade. The implementation of the programme is supervised by a Co-ordinating Council, composed of twenty-one Member States selected by the General Conference of Unesco, which studies proposals for developments of the programme, recommends projects of interest to all or a large number of countries, assists in the development of national and regional projects and co-ordinates international co-operation.

Promotion of collaboration in developing hydrological research techniques, diffusing hydrological data and planning hydrological installations is a major feature of the pro- gramme of the IHD which encompasses all aspects of hydrological studies and research.

Hydrological investigations are encouraged at the national, regional and international levels to strengthen and to improve the use of natural resources from a local and a global perspective. The programme provides a means for countries well advanced in hydrological research to exchange scientific views and for developing countries to benefit from this exchange of information in elaborating research projects and in implementing recent developments in the planning of hydrological installations.

As part of Unesco’s contribution to the achievement of the objectives of the I H D the General Conference authorized the Director-General to collect, exchange and disseminate information concerning research on scientific hydrology and to facilitate contacts between research workers in this field. T o this end Unesco has initiated two collections of publica- tions, ‘Studies and Reports in Hydrology’ and ‘Technical Papers in Hydrology’.

The collection ‘Studies and Reports in Hydrology’, is aimed at recording data collected and the main results of hydrological studies undertaken within the framework of the Decade as well as providing information on research techniques. Also included in the collection will be proceedings of symposia. Thus, the collection will comprise the compila- tion of data, discussions of hydrological research techniques and findings, and guidance material for future scientific investigations. It is hoped that the volumes will furnish material of both practical and theoretical interest to hydrologists and governments partici- pating in the I H D and respond to the needs of technicians and scientists concerned with problems of water in all countries.

Preface

Unesco and the International Association of Scientific Hydrology (IASH) have together undertaken the implementation of several important projects of the I H D of interest to both organizations, and in this spirit a number of joint Unesco-IASH publications are envisaged.

Similar co-operation has been established with the World Meteorological Organization (WMO); the present report is one of the joint U n e s c o - W M O publications which are planned.

Contents

Foreword

1 Introduction

1.1 Purpose and scope

1.2 Elements of SAPHYDATA 1.2.1 Schematic of SAPHYDATA 1.3

1.4 Organizational aspects

Determining the need for water data References

2 Description of different systems characteristics and evaluation of effectiveness

2.1 2.1.1 2.1.1 .I 2.1.1.2 2.1.1.3 2.1.2 2.1.2.1 2.1.2.2 2.1.2.3 2.1.2.4 2.1.2.5 2.1.3 2.1.3.1 2.1.3.2 2.1.3.3 2.1.4 2.1.4.1

Observing and measuring subsystems Surface water investigations

Measurement of stage

Discharge measurements and ratings Sediment discharge

Selection of water-quality parameters Level of effort within the network

Automated systems for recording water-quality parameters Systems using potentiometric sensors

Systems using resistance-type sensors Eutrophication of lakes

Data needs Survey methods

Selection of meteorologic data relevant to hydrology Water quality

Lakes, impoundments and estuaries

Meteorological observations

11

13 14 15 15 18 18

19 19 19 20 21 22 22 24 26 26 28 28 28 29 29 30 30

Contents

2.1.4.2 2.1.4.3 2.1.4.4 2.1.5 2.1.5.1 2.1.5.2 2.2 2.3 2.3.1 2.3.1.1 2.3.1.2 2.3.1.3 2.3.1.4 2.3.1.5 2.3.2 2.3.2.1 2.3.3 2.3.3.1 2.3.3.2 2.3.3.3 2.3.4 2.4 2.4.1 2.4.2 2.5 2.5.1 2.5.2 2.5.2.1 2.5.2.2 2.5.3 2.5.3.1 2.5.4 2.5.4.1 2.5.4.2 2.5.4.3 2.5.4.4

Meteorological factors of prime importance to hydrologists Advances in instrumentation

World-wide meteorological systems General consideration on remote sensing Remote sensing application to hydrology Research and development

Communication and coupling subsystems Computing subsystems

Processing and analysis of data

Computation and preparation of records Manual computation

Automatic computation Analysis of water-quality records Meteorological and other records Processing centres

Computer hardware

Algorithms for computer processing of water data Example of primary computation of streamflow data Examples of processing of water-quality data Availability of algorithms for data processing Hydrologic models

Publication of data

Automated data storage and retrieval Introduction

Assessment of technical capabilities of countries for implementing and using S A P H Y D A T A

Display and archiving subsystems

Methods of evaluation of the effectiviness of SAPHYDATA

Specific requirements for S A P H Y D A T A Requirements for operational use Effectiveness of S A P H Y D A T A Computing cost effectiveness

Evaluation of the manpower resources and availability of computers Planning and evaluating new information systems

Plotting of discharge measurements Evaluation of alternatives

Costs and cost effectiveness

References

3 Examples of systems adapted to different countries and situations

3.1 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.3 3.3.1 3.3.1.1 3.3.1.2 3.3.1.3 3.3.2

General considerations

The Hungarian National Water Authority The Hungarian hydrologic network Hydrological information service

Ground-water network and survey of springs

Other observations in representative and experimental areas Yearbooks

Working groups for data collection and processing Nordic co-operation within S A P H Y D A T A

Working group No. 4 (SAPHYDATA)

Relationship between SAPHYDATA, hydrochemistry and isotopes S A P H Y D A T A and the soil moisture working group

Summary of the Nordic co-operation

30 31 32 32 33 34 35 38 38 38 39 39 39 39 40 40 40 41 41 41 44 44 41 47 41 41 41 48 48 49 49 49 49 52 52 52 54

55 56 56 56 51 58 58 59 59 59 60 60 61

3.4 3.4.1 3.4.1.1 3.4.1.2 3.4.2 3.4.3 3.5 3.5.1 3.5.2 3.5.3 3.5.4 3.5.5 3.6 3.6.1 3.6.2 3.6.3 3.6.4 3.6.5 3.6.6 3.7 3.7.1 3.7.2 3.7.3

The Ohio River Valley Water Sanitation Commission (ORSANCO) System The O R S A N C O information system

Manual versus automatic monitoring Data compilation and appraisal Cost of monitoring

Appraisal of the robot monitor General considerations Automated data processing Automatic computation of runoff Data storage and publication Conclusions

Introduction

Present division of responsibilities Data collection network

Future requirements

The proposed national hydrometeorological data-processing system Concluding remarks

Automated hydrological data processing in the U.S.S.R.

Hydrometeorological data processing in the United Kingdom

A global system for the collection, transmission and processing of data:

the World Weather Watch: its implications for water information systems Introduction

World Weather Watch

Hydrological data and the World Weather Watch References

Selected U.S.S.R. references

61 61 62 62 63 63 64 64 64 65 66 66 61 67 61 67 68 68 69 69 69 70 70 71 71

Selected WMO references 72

Foreword

Historically, man first obtained his water wherever he found it-from pools, lakes, brooks and rivers-and in the early stages of human development these sources were almost always more than adequate for his limited demands. In drier climates where surface waters were less abundant, our ancestors learned to dig shallow wells down to the water-table, and these too helped to take care of water needs in many parts of the world.

Then as communities grew and agricultural practices developed, it became necessary to deliver larger quantities of water and man turned to canals and pipelines and aqueducts to satisfy these demands. The ancient civilizations of Mesopotamia and Egypt were assured a continuing supply of water from the Tigris-Euphrates and Nile rivers. These rivers have their origin in the snow-clad peaks in Asia Minor or in the highlands of East Africa.

These ancient civilizations never completely understood the source of the water, particu- larly the source of the Nile, but did understand the cyclic appearance of floods and droughts. They ascribed this cyclic behaviour to their gods, but were rational enough to develop a primitive technology to utilize the flood waters to develop irrigated agriculture.

Although these and succeeding civilizations rose to great heights and then passed from the historical scene, their technology was transferred to other civilizations in the Far East and Europe.

The hydraulic engineering works of the R o m a n Empire were outstanding and call for mention even in the briefest review; but there followed a long period of neglect and decay when the necessities of life these works had served were provided for by activities on a much smaller scale. Somewhat similar chains of events have occurred in some other areas.

Much later, developments in applied hydrology, notably in the Po valley and in the Netherlands, with also the activities of Dutch draining engineers, under Royal Charter from Charles I, in the marshlands and fens of England, preceded the birth of scientific hydrology in the seventeenth century. The renewed interest in science and natural resources in general, which included inquiry into the nature and occurrence of water on the surface and underground paved the way for the beginning of the industrial revolution in the eighteenth century. With the invention of the steam engine and its early development to pump water from mines to increase production came the corollary development of devices to measure and record streamflow and the fluctuations of springs and underground waters. By the middle of the nineteenth century the basic principles of physics and chemistry had been applied to the measurement of the water res0urce.l Governmental and private

1. A useful history of hydrology is now available for the reader w h o seeks fuller understanding of these developments serving basic requirements for advanced civilizations: Asit K. Biswas, History of HydroIogy, Amsterdam and London, North Holland Publishing Co., 1970.

organizations were measuring the volume of flow for power development and the construc- tion of dams. With the development of the science of bacteriology, the relationship of water-borne disease to public health was identified and water chemistry became an impor- tant foundation of the industrial revolution by providing a healthy urban environment whereby people and machines could be brought together to increase productivity and living standards.

Finally, in modern times, came the large dams and reservoirs and the deep high-capacity water wells that are such integral parts of today's water-resource developments. All of these methods, from simple river intakes to canals to the high dam, are still in use all over the world, and together form the basic pattern of modern water-supply systems.

The first half of the twentieth century saw the development of numerous national programmes to measure and record the water resource. In developed and in developing countries, organizations were established to determine the extent, volume, and quality of fresh-water resources in order to plan and manage them. In addition to national pro- grammes, every municipal agency supplying water for domestic and industrial use is engaged in quality-control programmes. These programmes usually involve disinfection and treatment of the raw water and water-quality surveys to seek out better supplies of water which would reduce the cost of water to the users and ensure the well-being of the people.

During this period there has developed an advanced technology for measuring and recording changes in the supply of fresh water. This technology is international in scope and application. Problems tackled and solved in the developed countries have application to problems currently being attacked in the developing countries.

This report discusses the status of the current technology available to assess the water resources. A brief survey is made of the application of new technology, particularly com- puter technology, to water-resource problems. In addition some political and social needs are discussed and some of the organizational structures designed to carry out water- resource assessment programmes are described.

The Panel on Systems for the Acquisition, Transmission and Processing of Hydrological Data (SAPHYDATA) wishes to acknowledge the help of many hydrologists who con- tributed directly and indirectly to this work. Although members of the Panel,' the Unesco Secretariat of the International Hydrological Decade and the Hydrology and Water Resources Department of the World Meteorological Organization wrote most of this report, other authorities made important contributions. The Panel wishes to express its thanks to these individuals and organizations.

1. J. Jacquet (Chairman), L. Raabt, E. Berntsen, V. J. Grigoriev, 0. Haszpra, G. W. Whetstone.

1

1.1

Introduction

Purpose and scope

The purpose of this work is to summarize the current state of knowledge on water-resource information systems, and, in particular, systems which acquire, transmit and process hydrologic data (SAPHYDATA). The term ' SAPHYDATA' is used to denote advanced data acquisition and processing techniques and procedures available to national authorities to provide them with adequate knowledge and information on the time and space distribu- tion of the various elements of the hydrologic cycle. As conditions are different in many countries, both in the physical distribution of water resources and in the stage of resource development, a variety of information systems may be conceived. This work provides authorities responsible for the direction of information systems with general information on systems that have been proved successful in many different environments, or are cur- rently under development as technically practical schemes.

It is stressed that this work will not provide the reader with the outline of standard data systems that can be universally applied, but rather with the basic background infor- mation on the current state of the art for selected water-information systems that serve both general resource development and special-purpose objectives.

Some estimates of cost of collecting different types of data have been included in this work. While these costs are based on currently available information, they may vary considerably from one locality to another. They should therefore bz interpreted as to their order of magnitude and not their absolute value.

Included in this work are reference lists of publications on the acquisition, processing, storage and publication of water-resource data. The authors have endeavoured to include only the latest publications on this subject and those which receive the widest distribution within the water-resource profession.

The reader, however, should be aware that with rapid advances in technology, there is often a considerable period of time between the initiation of a new system of data collec- tion or data processing and the presentation of the technical details in a formal publication.

Often regional authorities and national organizations in the water-resource data field prepare internal working documents primarily designed to train professionals inside and outside their organization (United Nations Economic and Social Council, 1968). Water authorities or administrations contemplating changes in methodology or improvement in the collection of water data and related information services should contact some of the principal organizations through normal channels to determine the present state of the art.

1.2

Elements of SAPH YDATA

The hydrologist is concerned with applying scientific knowledge, professional education, judgement, initiative and perseverence in developing information on water resources.

This is accomplished through the use of natural resources, facilities, available funds, and the capabilities of technology to meet stated objectives of a water-resource development scheme. Briefly, the hydrologist undertakes to produce certain practical results-stream- flow data for example-under the restrictions of existing circumstances. His stock in trade includes state-of-the-art technology, imagination concerning future developments, and the know-how to build components and techniques into a satisfactory working system. In fact, he has many well-developed and extensive segments of technology at his disposal (World Meteorological Organization, 1965). These component technologies are concerned with devices and technologies that fall into four principal classes.

Observing and measuring subsystems that contain sensors, the devices that receive states of physical or chemical quantities as inputs and produce signals representing these states as output.

Communications and coupling subsystems that transmit signals among information sub- systems, i.e. from the observational system to the recording system. Coupling subsystems that modify output signals from one subsystem so that these signals are suitable for inputs to other systems. An example would be an analogue recorder. Different arrange- ments of these subsystems can be found.

Computing subsystems that receive one or more independent signals as inputs, carry out logical operations, and produce outputs that represent information derived from the input. All aspects of data processing, whether manual or automated, are computing systems.

Display and archiving subsystems that provide direct visual indications and permanent records of signals and the information with which these signals are associated. Year- books of basic data are the simplest form of a display or archiving system. A magnetic tape or disc archive system is capable of transforming into display systems in many forms.

Each of these four categories is connected with different areas of technology. For example, communication subsystems include all the techniques of postal services, telegraphy, tele- phones, radio and radar. Indeed, certain hydrologic information systems may include transcontinental telephone lines or million-mile radio links from earth to space vehicles.

O n the other hand, communication within a water-resource data system may rely on little more than postal services.

Coupling subsystems are relatively specialized equipment that deal with such com- ponents as amplifiers, transformers, analogue-to-digital converters, data-storage system, etc. The water-stage recorder is a coupling system.

Display and archiving devices have many forms, with analogue and digital presentation ranging from printed yearbooks to high-speed cathode-ray tubes and electroluminescent figures.

Computing subsystems are the basis for a major industry supplying both analogue and digital computers that operate over a wide range of speeds, capacities and complexities.

It is certain that substantially any hydrologic data-processing requirement of practical importance can be fulfilled by currently available techniques. The differences among the various computer technologies lie in the capacity and processing speed for given invest- ments. Very large and expensive computer installations exist today for solving complex hydrologic problems, and very small units to deal with complex but specialized situations associated with routine data processing.

Because electrical signals are especially suitable for representing any kind of hydrologic data, signals with low power levels can be transmitted in many ways over short and long distances. They are easily adapted for rapid processing. For these reasons, electronic

Introduction

techniques are very widely applied to hydrologic data systems. Recent advances in the development of electronic computers will surely continue to force water-resource data systems towards a greater reliance on electronics (Unesco/IAHS, 1969).

The really difficult problems of SAPHYDATA involve the balancing of benefits from the information obtained against the funds and other resources that must be made available (see section 2.5). At the present time, data systems to sense and interpret the hydrologic cycle in terms suitable for controlling interactions are just beginning to demonstrate their usefulness; however, it is only a question of time before complete coverage networks will send water information to central computers and display centres from which fast, effective decisions may be made on proper actions to correct or control undesirable situations. The next ten years will surely be decisive for hydrologists who carry the responsibility of dealing with this portion of the human environment.

1.2.1 Schematic of SAPHYDATA

The schematic flow chart (Fig. 1 .l) shows the flow of data through a typical information system. Field data flows from the observation and measuring subsystem through the recording subsystem to the data-processing subsystem and then is distributed after reduc- tion or analysis to the users. The following sections of this chapter briefly describe the philosophy of S A P H Y D A T A . In addition there are some comments on the uses of basic data.

1.3

Determining the need for water data

O f great importance in the long view are the engineering applications to be made of the data collection, provided the data are systematically stored and are readily available for further analyses as a research tool. It should never be the intent to make the storing of data an end in itself though in the past because of cumbersome manual methods, this has in fact often taken a disproportionate share of the total effort. A data system should be alive and responsive to the needs of the engineering and research communities by providing all the information available that bears on a particular problem.

The supervisors of the basic data programmes, both when functioning as archivists and, especially, as data retrieval experts, should be in continuous and direct communica- tion with users of data. Evaluating the actual uses of data may convey significant infor- mation to guide the planning and operation of basic data storage, retrieval and display.

The summarized results of inquiries made on data use by one service programme (Whetstone and Schloemer, 1967) are given in the diagram (Fig. 1.2). The largest category contains those uses that are related to population, such as water supply and pollution abatement. The second category contains those uses related to floods and drainage prob- lems, such as flood control, forecasting, highway bridges, and land drainage. Irrigation is the principal use in the third category.

Figure 1.3 shows the shifts in the relative weights among the several uses over the past forty years between sampling of user requirements. Power and navigation, which in the 1920s were a significant influence on the basic data programme, are now relatively minor because of major changes in power development and transportation, that is, an increase in the use of thermal power and an increase in air transport. These shifts in purposes of the services provided by the basic data programme correspond to changes that have occurred in the engineer’s needs for data.

The diagram shows an upward trend in the proportion of effort upon the total popula- tion factors and the general decrease in data services for water power and navigation.

In the earlier period there was less contrast among the several activities, the population groups, floods and irrigation, and even water power all being about the same weight.

I ^STORl

-

DISSEMINATING

INTERNAL A N D CI COLLECTING AGENCY

I 1 EXTERNAL TO THE

~I I

4 I I I

I

COMPUTATION MANi?ULAT@N

DECISION MAKING

RESOURCE DEVELOPMENT RESOURCE M A N A G E M E N T

EXPLANATION

-

c-- +

PLANNING A N D PROGRAMMING

AREA OF MUTUAL IN7EREST TO THE DATA PROCESSING A N D DATA ACQUISITION ACTIVITIES

C O M M U N ICA.TION

RADIO .MICROWAVE

.TELEPHONE TELEGRAPH MAIL MESSENGER

FIG. 1.1 Schematic description of the major elements of SAPHYDATA.

DISSEMINATION

PUBLICATION MICROFORM PRINTOUT MANUAL OUTPUT MACHINE COMPATIBLE

Introduction

FIG. 1.2 Approximate distribution of service of basic water data, in a developed country, 1969.

FIG. 1.3 Example of distribution of uses of basic water data for a developed country, 1928 to 1969.

100

80

z

I- 3 CL I- CI I-

z

m 60

C"

5

-

U CL w L

20

0

I

I I

INavigotion

1

1930 1940 1950 1960 1970

Today, however, in an age of almost universal urbanization, the population group makes up about one-half of the programme. Projected population data niust be used to estimate the magnitude of future data requirements for water resources development and management.

1.4

Organization a1 aspects

The organizational problems associated with hydrologic data acquisition have been pre- viously described in a W M O technical note (World Meteorological Organization, 197 1) and were discussed at the Quebec Symposium (WMO/IASH, 1965). There are at least two schools of thought on the subject. In some countries separate organizations have been developed to handle meteorological and hydrologic data information. In other countries these services m a y be carried out by agencies having other activities, such as resource development, as their primary mission. There can be no established pattern and no general organizational rules laid down with the exception in the case of developing countries that data collection activities should be performed initially by the agency having the most interest in the data. It is quite probable that in developing countries the large action agency would have substantial resources with which to carry out the task efficiently-especially the computer hardware and telecommunications facilities, with which to operate the system.

References

BISWAS, Asit K. 1970. History of hydrology. Amsterdam, London, North Holland Publishing Company.

UNITED NATIONS ECONOMIC AND SOCIAL COUNCIL. 1968. Fifth biennial report on water resources development. New York, United Nations, 126 p. (Off. Records., 44th session, suppl. 3.) UNESCO/IASH. 1969. The use of analog and digital computers in hydrology. Proceedings of the

Tucson Symposium, 1966. Paris, Unesco, 2 vols. (Studies and reports in hydrology, 1.) WHETSTONE, G. W. ; Schoemer. 1967. National environmental data collection system for water

resources development. In: International Conference on Water for Peace. Volume 4. Washing- ton, D. C., United States Government Printing Office.

WORLD METEOROLOGICAL ORGANIZATION. 1965. A design of networks. In: Guide to hydrometeo- rologicalpractices, Ch. 3, 17 p. Geneva, WMO. (No. 168, T.P. 82.)

W M O / I A S H . 1965. A symposium on design of hydrological networks, Quebec. Gentbrugge.

(IASH publications no. 67.)

WORLD METEOROLOGICAL ORGANIZATION. 1971. Machine processing of hydrometeorological data.

Geneva, W M O . (Technical note no. 115.)

-

2 Description of different

systems characteristics and evaluation of effectiveness

In this section, consideration is mainly given to problems of acquisition and processing of data concerning hydrological and relevant meteorological parameters which present a high range of variability in time or space and require a great frequency or density of observations. The different techniques used for solving these problems (manual, auto- mated, mixed) are explored and grouped according to the four principal classes of SAPHYDATA elements mentioned in Chapter 1.

2.1

Observing a n d measuring subsystems

2.1.1 Surface water investigations

Streamflow, water levels, suspended sediment and water quality are the most important parameters used to measure and quantify the surface water resources for both resource planning projects and management activities. The task of measuring and recording these parameters is well documented in the literature. In the following, attention is directed mainly to less familiar material and techniques in connexion with the use of automatic procedures.

2.1.1.1 Measliveinerit o j stage

Measurements of stream stage are used in determining records of stream discharge and records of stream stage are useful in the design of structures affected by stream elevation, or in the planning of the use of flood plains.

A record of stage can be obtained by systematic observations on non-recording or recording gauges. The non-recording gauge most commonly used is the vertical graduated staff gauge. The gauge is read by a local observer on a fixed schedule.

The advantages of the non-recording gauge are the low initial cost and the ease of installation. The disadvantages are the need for an observer and the lack of accuracy of the estimated continuous stage graph sketched through the points of observation. For long- term operation the advantages of the recording gauge in subsequent data processing steps far outweigh those of the non-recording gauge.

Stage is usually automatically sensed and recorded by a float in a stilling well that is connected to the stream by intake pipes.

Stage may also be sensed by a gas purge system known as a bubble gauge. This system does not require a stilling well.

The bubble gauge is used primarily at sites where it would be expensive to install a stilling well. It is also used on sand-channel streams because the gas tends to keep the orifice from being covered with sand and the tube may be easily extended to follow a stream channel that shifts its location. However, the float-stilling well installation is cheaper to install at most sites and its performance is more reliable than is that of the bubble gauge. The two systems have about the same accuracy-0.2 centimetres. The choice of systems thus depends on the characteristics of the site.

Both strip-chart and digital-tape water-level recorders are in general use for the con- tinuous recording of water levels. Either recorder may be actuated by the float or bubble- gauge system.

A strip-chart recorder produces a graphic record of the rise and fall of the water surface with respect to time. Continuous recorders will operate unattended for long periods of up to 60-90 days, and provide a very satisfactory record of stage.

A digital stage recorder punches coded values of stage on paper tape at preselected time intervals. A time interval of 15 minutes is normally used. A digital recorder, used in different countries, is battery operated and will run unattended for periods of 60-90 days.

The code can consist of four groups of four punches, each with the four punches repre- senting 1,2,4, and 8 in each group. The punching of a stage requires only 2 mm of paper tape advance. The recorder is actuated by a cam on a battery-driven mechanical clock.

Magnetic tape digital recorders are also coming into operational use.

Digital recorders are gradually replacing strip-chart recorders at streamflow stations.

The analogue chart and digital recorders are about equal in accuracy, reliability and cost, but digital recorders are compatible with the use of electronic computers in computing dis- charge records. This automated system offers economy and flexibility in the computation- publication process as compared to manual methods associated with graphical recording.

2.1.1.2 Discharge measurements and ratings

Discharge measurements are made at streamflow stations to define the discharge rating for the site. The discharge rating may consist of a simple relation between stage and discharge or a more complex relation in which discharge is a function of stage, slope, rate of change of stage, or other factors.

Discharge measurements are normally made by the current-meter method, which con- sists of determinations of velocity and area in the parts of a stream cross section. Measuring weirs are also used for determining water discharge from direct measurements of the head of water flowing over the crest. However, indirect methods are frequently used in determining flood peak discharges when it is impractical to measure the peak discharges at the time of occurrence owing to local conditions. These methods utilize hydraulic equations in conjunction with the information on channel characteristics and flood marks obtained in a field survey after the flood event.

Discharge measurement may also be made by the dilution method. This method depends on determination of the degree of dilution of an added tracer solution by the flowing water.

Stage-discharge relationships are rarely permanent because of changes in the stream channel such as scour and fill, aquatic growth, ice, debris, or changes in bed roughness.

The stability or instability of the stage-discharge relation determines the frequency of discharge measurements that are necessary to define the relation at any time.

If highly unsteady flow or variable backwater exists at a gauging station the discharge rating cannot usually be described by stage alone.

The discharge under these conditions is a function of both stage and the slope of the energy gradient, which is approximated by the slope of the water surface between two points on the stream. Stage-fall-discharge ratings are usually determined empirically from observations of discharge, of the stage at the base gauge, and of the fall of the water surface between the base gauge and an auxiliary stage gauge downstream.

Description of diferent systems characteristics

If the flow is very unsteady, as for example in a tidal reach of stream channel, the acceleration head will govern the energy slope. Under these conditions unsteady-flow equations must be used to describe the variation of discharge with time. Detailed descrip- tions of these techniques are given in the specialized literature.

2.1.1.3 Sediment discharge

Sediment discharge is the rate at which dry weight of sediment passes a section of a stream, usually expressed as kilogrammes per unit of time. The term ‘suspended sediment dis- charge’ is sometimes used to denote only that weight of material in suspension in the water passing a given point. Present techniques for determining the rate of discharge and the concentration of sediment involve the measurement of the ratio of the weight of the water sediment mixture, expressed as milligrammes per litre (mg/l), the measurement of water discharge and the load which is the product of the water discharge and concentration.

The prediction of future rates of sediment discharge is the most important purpose to be served by a sediment network. In addition, special studies may also be required from time to time to evaluate ‘erosion control’ programmes, to measure sediment transport within and from areas experiencing rapid urban or ex-urban development, and to evaluate the stress on channels from increased runoff from upstream developments.

The sediment sampling programme can be considered to fall into one of three classes.

The first is the continuous measurement of sediment discharge where the amount of sediment as measured by suspended-sediment samples is computed and recorded on a daily basis. A set of suspended-sediment samples should represent the sediment concentra- tion of the stream at the time of the sample and, therefore, the data indicated by the sample must be extended backward and forward in time. The length of time applicable to a given sample depends on the time of the previous and next sample and whether or not there are important changes in stream conditions.

A reasonable programme for the recording of daily suspended sediment discharge then requires not only the use of proper equipment to obtain representative samples but also a very sophisticated set of objectives and judgement with respect to the data. If the objective is to satisfy the need of a user withdrawing a relatively uniform amount of water then the major emphasis should be on sediment concentration of the flow, and the samples would be spaced rather uniformly in time. If the objective is to determine the sediment load or tonnage of sediment moved by the stream then it may be desirable to sample the low flow periods once a week or on days of change and sample two or three times a day during high flow periods when most of the sediment is transported. The thunderstorm type of sediment hydrograph is perhaps the most difficult to construct adequately because of the effects of uneven precipitation in the basin and because of the ever changing environmental factors, many of which can be related to the season of the year and to land use.

The second type of sediment sampling programme is classified as a partial record activity. This is essentially the same as the daily record except that data are obtained only during selected times of the year based on a predictable periods of significant sediment discharge, usually during periods of high storm runoff. The equipment used and the timing of samples for the partial record would be the same as for the continuous record. This type of programme measures the major part of the sediment discharge and defines the runoff during unusual runoff events.

The third programme is the periodic sediment record that may be represented by one of a large variety of sample techniques and timing. Perhaps the most common programme would be the collection of samples for a sediment discharge measurement each time a technician visits the station-once every two weeks or once a month with perhaps more frequent observations during flood periods. These kinds of data are published on an

‘instantaneous’ basis as a list of the water discharge, the sediment concentration and sediment discharge.

A series of ‘reconnaissance’ measurements should usually be made prior to the estab- lishment of any of the three programmes to obtain comparative information on conditions likely to be encountered in the future. Even after a programme is started, it should be expected that operational adjustments willbe required with respect to equipment, sample timing, or even measurement location, especially in areas of changing land use.

Sometimes the requirements of any of these programmes may be such that sediment must be measured in terms of total load, in which case it willbe necessary either to sample the sediment at a site where it is suspended into the sampling zone by natural or artificial means, or to calculate the amount of the unmeasured sediment. As one would expect, any of the three programmes requires a wide range of sampling arrangements determined by climate and drainage basin characteristics, especially size. The data needs and the operation of a sediment measuring station on the Amazon River, for example, is vastly different from that of a small channel draining a ten-acre basin in an area under urban development.

2.1.2 Water quality

Water quality is becoming an increasingly important part of hydrologic data collection programmes. The rapidly expanding utilization of the water resource coupled with an increased use of surface and ground water for the disposal of waste products has created a complex measurement and interpretation problem for hydrologists. The complexity of the problem is immediately apparent in reviewing the voluminous literature on water quality which has appeared in recent years. A review of published literature on analytical methods for water analysis made in 1969 (Fishman and Robinson, 1969) listed 664 methods which had been developed in a two-year period, 1967-68.

2.1.2.1 Selection of water-quality parameters

Any design for a water-quality network faces the immediate question : What parameters should be included in the measurement programme that will provide a broad base of information for general use ? About sixty chemical, physical, and biological properties are pertinent to various uses. (See Table 2.1.) It must follow that the design or plan for measurement selected willbe flexible so that the selected or key parameters measured will lead logically from one level of activity to the next higher as measured by parameter diversity.

The following parameters are recommended for measurement in hydrologic water- quality networks.

Chemical parameters : Physical parameters : Biological parameters : dissolved solids colour biological diversity dissolved oxygen turbidity coliform.

hardness temperature

alkalinity radioactivity

nitrate odour

phosphate. P H

sediment.

All of the parameters recommended for inclusion in the water-quality network are per- tinent to three or more uses of water: i.e., domestic, industrial, and irrigation. They are all relatively simple standard determinations which can be made with a minimal amount of equipment.

Description of different systems characteristics

TABLE 2.1 Tests of water to define water quality for various uses

Property or Property or

constituent A1 B2 C 3 D 4 E5 constituent A1 B2 C3 D4 E5

Total acidity Immediate acidity Potential free acidity Alkalinity

Aluminium Arsenic Barium Boron Bromide Calcium Carbon dioxide Chloride Chlorine residual Hexavalent Chromium Colour Copper Density Fluoride Hardness Noncarbonate

hardness Iodide Iron Ferrous iron Lead Lithium Magnesium Manganese chromium

x x x x

x x X

x x ^X

x x x x x

x x x x x

X X

X X

x x

X X

x x x x x

X X

x x x x x

X X

X x x

x x ^X

X X

X

X x x

x x x x x

x x x X

X X

x x x x

X X

X X

X

x x x x x

x x x x

Ammonia nitrogen x X

Nitrate nitrogen x x x x

Nitrite nitrogen x ^X

Organic nitrogen x X

Oils and waxes x x Biological oxygen

Oxygen dissolved x x x x

p H value x x x x x

Phenolic material x X

Orthophosphate x x x x

Phosphorus x x

Potassium x x x x

demand ^X

Residual sodium

carbonate X

demand x x

Chemical oxygen

Selenium X X

Silica x x x x

Sodium x x x x

Percentage sodium X

Sodium adsorption

ratio X

Specificconductance x x x x x

Sulphate x x x x x

Sulphides X x x

Turbidity x x

Viscosity X

Zinc ^X X

I. (A) Tests for determining potability or pollution of water for domestic and related uses.

2. (B) Test for determining probable suitability of water for industrial use.

3. (C) Tests to determine the general suitability of water for agricultural uses.

4. (D) Tests that provide data for studies in the natural sciences (a use of data that does not involve a

use of the water).

5. (E) Tests pertinent to three or more uses of data.

Clremica1 parameters. Dissolved substances include both inorganic and organic com- pounds, dissolved gases, and radioisotopes. Dissolved inorganic substances include the commonly occurring mineral constituents such as calcium, magnesium, sodium, and potassium. Salts of these elements in varying concentrations determine the fitness of water for a wide range of municipal, industrial, and agricultural uses. Although normally considered to be a physical property, p H is a measure of hydrogen ion concentration and is an important water-quality parameter.

The chemical parameters, dissolved solids, hardness, and alkalinity, are major water- quality indicators and are useful in making regional comparisons.

Dissolved gases in water include oxygen, carbon dioxide, nitrogen, hydrogen sulphide, methane, ammonia. Of these, dissolved oxygen is the most important and is used as an index of dissolved gases for network design purposes.

Physical parameters. Of the physical properties temperature, colour, odour and turbidity are the most significant. Others include density and viscosity. Non-soluble, particulate substances in streams include inorganic sediments, natural organic materials (coal particles, leaves, and other plant debris), and municipal and industrial wastes. Of these, the municipal wastes decompose relatively quickly and diminish relatively rapidly below their point of entry. Their effects on water quality bear mostly on the dissolved constituents and biota. They are taken into account in the measurement of corresponding parameters and consequently the hydrologic network for particulate materials will be organized to describe mostly inorganic sediments.

Biological parameters. Biological diversity in a stream community is illustrated by such plant and animal organisms as bacteria, fungi, algae, diatoms, mosses, flowering plants, protozoa, worms, insects, snails, mussels, and fish.

Within the hydrologic network (including benchmark and vigil stations) there is a need to know the extent of highly diversified biological systems within the basin as a baseline for comparison with conditions after a stream is affected to some degree by the works of man.

2.1.2.2

Stations in the hydrologic network may be operated at several levels of effort. In the early stages, measurements indicated in the foregoing section willbe prevalent. As data are collected, analytical studies made, and knowledge increased, the emphasis may change.

These changes may result in an expansion of effort to specific parts of the water-quality regime such as the chemical, physical, or biological, for better definition of variability and a corollary increase in frequency of sampling. This would require additional levels of effort where anomalous situations may be found due to certain environmental conditions.

Variability of the measured parameters willdetermine the level of effort required to define the causative factors. Extreme variations in dissolved solids would require a detailed examination of individual ions to determine the cause and relate the variability to a specific or general terrane characteristic. Rapid fluctuations in turbidity would lead logically into a sediment programme to determine quantities of suspended material, particle size, and mineral composition. Two additional levels of measurement are planned and illustrated in Table 2.2.

After the range in concentration has been determined and its relation to the terrane documented, the level of effort could be reduced to the initial general surveillance level.

Because streamflow varies considerably within a year, and from year to year, the con- centration of dissolved and suspended solids varies accordingly. The observation of water quality will also emphasize time-series measurements.

Level of efort within the network

Description of diflerent systems characteristics

TABLE 2.2 Level of measurement effort within the water-quality network

Level I

SURVEILLANCE

Level 11 INTENSIVE

Level 111 PROJECT

Chemical parameters:

Dissolved solids SiO,, Ca, Mg, Na, K, SO,, C1, F, B, Fe, M n

Li, Se, Br, I, S, SO, AI, As, Cr, Cu, Pb Hardness Ca, Mg, Fe, M n Ba, Sr, AI

Alkalinity (Acidity) HCO,, CO,, OH, H+, Buffering capacity. Immediate,

H!W4 potential, free acidity

Nitrate NH,, NO, Organic nitrogen

Phosphate HPO,, HZPO4

Physical parameters: Cliemical:

Colour Chloroform extracts, Infrared spectre of chloroform ether insolubles, extract and neutrals

water solubles

Odour weak acid-odour

bases-amines neutral strong acids

PH See ‘Alkalinity’

Turbidity To sediment network Radioactivity

Temperature

Biological parameters:

Biological diversity

Sr9”, Ra, U

Bacteria, fungi, algae, bryophyta, protozoa, nematoda, Pisces

B. coli Str. Faecalis Virus

Dissolved oxygen Biochemical oxygen

There is a certain relationship between levels of measurement effort and frequency of measurement. Because the intensity of water-quality problems may not be equal in all areas, certain measurements may be made at different levels of frequency, monthly, daily or continuous. For example, the time-series measurement of biological parameters may be on a different frequency schedule than those involving chemical and physical parameters.

The hydrologic factors which influence biological diversity are slightly different than those which influence quality. For example, the nature of the stream-bed community is largely determined by the following factors :

1. The velocity of the water;

2. The size, nature, and stability of the stream-bed;

3. Physical character of the water;

4. Chemical nature of the water;

5. The presence of stream-bank vegetation.

The sampling frequency for measuring biological diversity might be on a seasonal basis in order to obtain data applicable to a wide range of environmental factors.

Conversely, dissolved oxygen might be measured at several frequency levels during a particular time period. During the colder months when water temperatures are low and dissolved oxygen solubility is high, samples might be obtained at monthly intervals. In the spring and summer when the water is warm and the solubility of oxygen low and when there is increased biological activity either producing or consuming dissolved oxygen in the water, the sampling frequency required to define the environmental influences might be daily or even continuous.

The sampling in the water-quality network would be determined by the parameter variation and would not be imposed by fiat. A n increase in variability in one or two parameters requiring an increase in measurement and sampling frequency would not require a complementary increase of the same order of magnitude in the other parameters.

2.1.2.3

At the present time at least two different types of automatic water-quality sensing systems are available for water pollution studies. One type utilizes potentiometric sensors. In its basic form, it meets the needs of a simple in situ recording system that can be easily expanded to meet more complex data requirements. The second type uses resistance-type sensors for in situ monitoring in remote locations where only battery power is available.

Automated systems for recording water-quality parameters

2.1.2.4 Systems using potentiometric sensors

The heart of a typical potentiometric sensor system is a programmed, servo-drive unit (Fig. 2.1). It is designed to accept a maximum of ten channels of input from potentiometric sensors (dissolved oxygen, p H , etc.) and to automatically programme these inputs into a recording device. The unit consists of a measuring circuit for each channel, a programmer, a solid-state amplifier, and the drive unit.

Each channel has an individual, interchangeable measuring circuit to accommodate the variable inputs from the sensors. These circuits are precision resistor networks for voltage adjustments; thus, each circuit has individual span and zero adjustments. Circuits, up to the maximum ten channels, can easily be added to the system in the field. The ten circuits share a single amplifier.

Potentiometric sensors may determine water temperature, wet and dry bulb air tem- peratures, specific conductivity, dissolved oxygen, oxidation-reduction potential, p H , turbidity, sunlight intensity, wind velocity, and wind direction. The outputs of these sensors are linearly proportional to the variable being measured and are automatically compensated for temperature variations.

Description of different systems characteristics

t

21

2.1.2.5 Systems using resistance-type sensors

Several data sensors of the resistance type exist. Among them are sensors for water tem- perature, wet and dry bulb air temperatures, specific conductivity, and soil moisture.

2.1.3 Lakes, impoundments and estuaries

Lakes and impoundments together represent an enormous volume of fresh water io storage. These two types of surface-water bodies are similar in that their water retention times are relatively long. The estuaries, because of their great volumes of water available for cooling and waste assimilation and their usefulness as shipping lanes, have become centres of population and industry.

The importance of the quantitative and qualitative control of these water bodies is increasing as the ratio of available water to water need decreases. General quality degrada- tion follows eutrophication in lakes and reservoirs and salt encroachment from increased waste loading and fresh-water diversion have already affected certain estuaries significantly, and can be expected to affect others. Systematic collection and interpretation of hydrologic data are required to explain the nature and magnitude of the natural controls in such water systems, and to predict their trends in the variety of environments involved.

2.1.3.1 Eutrophication of lakes

Eutrophication of lakes is usually associated with the growth of large amounts of aquatic plants. These plants, grown in small amounts are beneficial. In large amounts they may seriously impair the quality of the water.

The cause of overabundance of aquatic plants seems to be excessive fertilization by dissolved nutrients.

The problems of eutrophication are not limited to lakes, but are important in rivers, harbours, and estuaries. What will be said about lakes willapply in some respects equally to these other surface waters. The areas and effects of eutrophication may be summarized as follows.

1. Water supplies : increased cost of treatment, taste and odours, colours, 2. Recreation: loss of boating, swimming, fishing, loss of property value, 3. Agriculture: toxicity, aquatic weed growth, clogged irrigation canals.

1. Domestic and industrial wastes (phosphorus and nitrogen);

2. Urban drainage;

3. Agricultural runoff (phosphorus and nitrogen from fertilizers);

4. Natural runoff;

5. Lake sediments;

6. Atmosphere (mainly phosphorus and nitrogen from rainfall);

I. Subsurface drainage.

1. Nutrient removal;

2. Diversion of water to streams below lakes;

3. Removal of weeds;

4. Dredging lake sediments;

5. Low-flow augmentation;

6. Zoning of watersheds.

increased temperature;

changes in types of fisheries;

The sources of plant nutrients promoting eutrophication are:

A m o n g possible control measures:

Description of digerent systems characteristics

2.1.3.2 Data needs

Throughout the world there are some two million fresh-water lakes, thousands of large impoundments, innumerable small impoundments and about one thousand major estua- ries. It would be very costly and, in fact, unnecessary to collect comprehensive hydrologic network data on all of these water bodies. A n acceptable alternative is to satisfy minimum hydrologic data needs on a representative sample of the water-body population, and to cover the remaining resources through reconnaissance and surveillance. Initial recon- naissance is particularly useful where existing data are limited or absent (e.g. for lakes), because it provides a basis for using modern sampling theory in selecting sampling points for more intensive network coverage. Periodic surveillance using key determinations is aimed at designing the basic network. If properly collected, basic network data should have transfer value; that is, they should lend themselves to prediction of behaviour of water bodies other than those being sampled.

The collection of data should be directed at measuring the natural aging processes of lakes (benchmark lakes) which willbe used to measure the changes brought about by use of lakes by man.

In addition to this general data collection plan, there is also occasional need for special project testing where network coverage does not provide all the information required at that particular place and time. A limited number of case studies may also be required.

These are long-term special project studies in which comprehensive data are collected.

2.1.3.3 Survey methods

For reconnaissance and surveillance one must use mass survey methods and rely on key determinations which provide maximum information at minimum cost, recognizing that this type of data collection sacrifices some precision in the interest of wide coverage.

Recently developed remote-sensing techniques such as aerial photography, infrared map- ping, and echo sounding, allow reasonably precise, rapid measurements of hydrologic data.

Selecting key determinations for the several water bodies depends to some extent on the relative importance of natural and cultural factors involved, and on the water charac- teristics of major concern. The major emphasis would be placed on terminal form and location in the water cycle of the nutrient solutes, nitrogen and phosphorus. Other impor- tant parameters requiring measurement include turbidity, odour, pH, redox potential and biological diversity. These measurements are the same as those proposed for the reconnais- sance level of the water-quality network.

In the case of large reservoirs, siltation rate, evaporation rate, and the relationships of inflow to volume to temperature provide most of the information needed. In a natural lake intended primarily for recreational use and domestic water supply, periodic measurements of such parameters as lake level, lake-bank population, and total organic and inorganic contents of the water, particularly in periods of low water, probably would be the most useful tools in assessing trends on a mass scale. Dissolved oxygen content and salt concen- trations at critical locations would be useful pieces of information for those estuaries which cannot be covered by more comprehensive basic network testing.

Such measurements would also document trends in hydrologic processes and eutro- phication in order to increase our understanding, for example, of the nutrient requirements of eutrophicatic or photosynthetic organisms.