WATER SUPPLY

The progress of technology has made it possible to supply urban regions with sufficient

WATER

QIíaT.TTV

WATER SOURCE

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— — PRICE L LvOLUME^J

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AGRICULTURAL USE

REMAINING QUANTITY OF WATER NECESSARY FOR OTHER SOCIAL, ECONOMICAL AND ECOLOGICAL REASONS

Figure 5.1 Urban water use system

Water supply

amounts of water, even if it has to be transferred over long distances. Moreover, today refined methods of treating water are used so that water which could not be used in the past because of low quality can now be used. Technological progress is also partly responsible for the increased water demand of modern society. Immigration to urban areas may necessitate a more rapid development of the water distribution system than is permitted by the supply available.

In this situation, water costs will increase and water management planning will have to consider a range of factors - social, political, environmental and hydrologlcal. This may in some instances, result in a decision to stop further suburbanisation.

The negative effects of the scattering of new human settlements in a country have to be pointed out because countries not yet at this stage can learn from the past mistakes in urban planning of other countries.

Urban growth has already been briefly discussed in an earlier chapter. The increase in urban population taken in conjunction with an increase in the amount of water used per capita has not only caused problems for water authorities but also brought about a competitive situation in the demand of water from rural areas. Hall (1974) questions if all the social and economic costs are greater or less than the cost of providing more water in lieu of reallocation. Moreover, are the marginal uses of water in the urban environment really higher in value for the national goals than their use in agriculture? What is the

relationship between the amounts of water used in urban and agricultural sectors? How much urban water use is equivalent to the use of a given volume of water on the farm? Current decisions on water allocation could be reversed by the answers to questions such as these.

Water for urban use is obtained principally from surface sources such as lakes or rivers and from groundwater sources such as springs or wells. An urban region is usually supplied from one or more water-works operated by a water authority. However, industries with a great demand for water very often draw upon their own water sources and they try to locate the plants where water is easily available.

Some of the socio-economic aspects that could be considered in the use of different kinds of water sources are that groundwater is generally of better quality than surface water and that the risk of disturbance in a water supply system based on groundwater sources is probably smaller than for one using surface water. For instance, pollution of surface water may rapidly reduce the quality of water, whereas groundwater reservoirs are not always so vulnerable. On the other hand, the effects of groundwater pollution may be much worse than that of surface water; the pollution of groundwater may not be known before long periods of time elapse between cause and effect, and the process of purification may be similarly prolonged.

It is important to remember the possibility of combined use of surface and groundwater.

Such an integrated use assumes an allocation process based on concise planning of activities (Kuiper, 1971). Such planning necessitates proper knowledge of hydrological processes.

Another possible source of water for urban regions is desalinated water which is already being used, especially in North Africa and the Middle East. However, the desalting costs have been significantly increased in recent years (to more than US$1 per m3) as the cost of energy has increased. The use of conventional sources will for a long time remain less costly. It is only when the demand exceeds the possible supply from optimally allocated conventional sources and when this water is used in the most efficient way that the use of unconventional (desalted) waters will be economically justified (de Marl, 1976). Also, known laws of physics seem to limit the possibility of a major break-through in costs

(Koelzer and Bigler (1975)). All desalting techniques use large amounts of energy. With the exception of solar processes (which are not highly promising for installations of appreciable size), this energy must be supplied by steam or generating plants. Even with an efficient energy system, the absolute minimum amount of energy needed, to perform the work of separation of water molecules from the ions in the saline water in order to convert saline water to fresh water, remains high.

Several other aspects of the possible use of desalinated sea water should be considered.

Nikitopoulos (1962) discussed the costs of transporting water from the coast, but because of the cost, he considered desalination would probably be unrealistic at long distances from the coast and only possible in areas where no conventional water resources are available.

Therefore urban areas at the centre of continents are not likely to be supplied by desalinated sea water. Notable here is the Sahel area in Northern Africa. Another aspect is the

environmental effect caused by the disposal problem. According to Koelzer and Bigler (1975)

Water supply

the volume of effluent from a 10 mgd plant will contain about 2O0O tons of salt residue daily.

This amount is not unrealistic as the largest plant in operation in 1971 had a capacity of 7.65 mgd.

A further problem is that an urban area solving its water demand problem by desalination will remain dependent on the continuous operation of such a desalination plant. An interruption caused by technical breakdown, or for other reasons, may give rise to catastrophic consequences for the urban area.

According to present water-demand tendencies, water distribution systems will probably call for an increased investment per capita for the following reasons (Grima, 1973):

1. higher per capita consumption

2. the need to develop less accessible sources of supply 3. urban sprawl (for instance longer distribution conduits,

larger lawns etc)

4. peak demand increases more rapid than average demand.

In addition to these reasons for increased investment per capita it should be noted that an augmented use of water in urban districts causes water treatment costs to rise.

Water supply problems in industrialized countries may considerably affect the nation's economy. In developing countries, especially in arid parts of the world, the provision of a safe supply of fresh water could have an enormous impact on social and economic development. But according to Feachem (1975), for the great majority of the world's

population who live in rural communities, or low-income urban slums, with grossly inadequate access to safe water, there is no possibility that available financial and human resources will provide them with the high level of water provision to which the people of many

developed countries have been accustomed. Because there is no immediate prospect of providing a significant proportion of low-income communities with high-grade water facilities, it is necessary to examine closely the goals of water supply in order that scarce resources may be allocated as efficiently and rationally as possible.

Feachem (1975) , also makes the important remark that during the last two decades, many studies concerning water supply schemes for developing countries have been carried out and that nearly all of these have indicated that water supply may be a necessary condition, but is never a sufficient condition, for development. Thus, water-supply development must be accompanied by a carefully designed package of complementary inputs if it is to achieve the goals stated.

In the planning and development of water distribution systems, complex processes are involved. Sometimes these may be well-handled by modelling. For instance, some kind of system dynamics may be used as in studies of the behaviour of complex social and physical systems. Grigg and Bryson (1975) have recently used simulation methods in a study of the Fort Collins system. The general programme proceeds according to the following steps:

1. Definition of goals (level of water service need in quantity, quality and location)

2. Collection of data (existing systems, population projections etc) 3. Study and formulation of the alternatives, eg

(a) alternative of objective (b) engineering alternatives (c) management alternatives (d) institutional alternatives (e) times and scale alternatives (f) location alternatives 4. Evaluation of alternatives 5. Selection of a plan

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Water supply

An example concerned with a developing economy is the model of the need for water-supply development in Puerto Rico discussed by Attanasi (1975). His model is especially interesting as it relates development and industrial patterns to water-resource investments. This relationship is shown mathematically by regression analysis. Attanasi found a significant relationship, over the nine year period considered, between changes in the income distribution and the pattern of water resources development.

In such a planning process, several different models may be used, eg, models for population growth and models for water use. Such models are, as a rule, adapted to a specific situation that exists in a particular region or nation.

The planning of a water-supply system necessitates that some essential basic data are properly known. First of all the available water resources have to be known, a knowledge that is acquired by thorough hydrological analysis. Secondly, a cost-supply relationship and the price-dependent water-demand should be determined.

McPherson (1976a) has suggested that these relationships are not clear:

'Investigations of relationships between price and demand, and metering and demand, have been handicapped by the limited amount of representative detailed demand data available in a usable form. For example, it is still not clear to what extent metering constrains demand in response to price.' 5.2.1 Problems of water allocation

The allocation of water resources may cause problems because the water can no longer be regarded as a free commodity. According to Goddard (1975) continued population and economic growth have caused the resources that once were free, or at least relatively so, to become scarcer and, consequently, more valuable. Thus, in allocating water for urban use the manager is faced with a situation of competition between different uses.

The problems and solutions of an efficient or optimal allocation of scarce resources should be analysed on the basis of economic efficiency and its associated concepts, such as opportunity costs, net benefits, externality analysis and consumer sovereignty, which are fundamental to valid analysis as long as economic efficiency is a social goal with respect to resource utilization (Goddard, 1971). Most economists advocate that the economic efficiency concept should be used in analysing allocation problems see, for example, Mishan (1972) and Baumol (1972), who also state that the net benefit concept should be the measure of performance.

The cost of water as well as its value play an important role among the social factors.

The cost of water may be defined as the cost per unit volume to make it available at a given flow, at a given time, and a given place. Likewise, the value of water can be defined as the maximum price per unit volume which we would be willing and able to pay, to obtain a given flow, at a given time, and at a given place; or the minimum price per unit volume which we would be willing to accept if someone proposed to take away from us a given flow, at a given time at a given place. It follows from this definition that if we quote a value of water we must also state precisely the circumstances under which this quotation is made.

(Kuiper, 1971).

Accordingly what should be determined and firially maximized is the net benefit or revenue less costs, in providing water to the users. The appropriate cost concept is the opportunity cost which, in most cases, is the same as, or approximately the same as, the production cost. More problematic is the revenue concept, the definition and measurement of which is the main theme of this report. This is so because the revenues cannot be measured solely in monetary terms. Social factors are very important and these can be both positive and negative.

5.2.2 Water demand and water use

The costs of water-distribution systems are comparatively easy to determine if the quantity to be withdrawn is known. Difficulties arise in the prediction of the water demand. In the industrialized countries demand is, to a limited extent, governed by the price. The

industrial demand, however, is more dependent on processing technologies. Technological break-throughs cause considerable changes in the withdrawal demands and also in the actual water use.

Water supply

The water demand of urban areas may be divided into three types, industrial, municipal and agricultural. Municipal demand may be subdivided into four types showing different price-demand relationships (see Figure 5.2):

1. residential demand 2. public demand

3. industrial demand (industries connected to the municipal distribution system)

4. leakage

TOTAL WATER DEMAND

_

AGRICULTURAL DEMAND

MUNICIPAL DEMAND

RESIDENTIAL DEMAND

PUBLIC DEMAND

T T

INDUSTRIAL DEMAND

LEAKAGE

INDUSTRIAL DEMAND

Figure 5.2 Schematic view of urban water demand

This subdivision is based on that of Berry and Bonem (1974). In a study for New Mexico they found that the per capita municipal water use was linearly related to the per capita income. Price, temperature, etc. had no significant influence on the water use. This result is not in conformity with the results obtained by Howe and Linaweaver (1967) . The main

reason for this is that the Howe and Linaweaver study was concerned only with residential water use whereas the Berry and Bonem study considered municipal water use as a whole.

5.2.3 Residential water demand and use

Residential water demand and use refer to water used for various activities mainly in

dwelling houses. The residential water use in developing countries is much less than that in industrialized countries. Dieterich and Henderson (1963) found in a WHO study of problems in 75 developing countries that only one-third of the urban population and less than one-tenth of the total population were supplied with piped water in or near their homes.

A study financed by the US Agency for International Development, in 1967, in a large provincial area of a developing country with about 6.8 million urban population showed similar results:

1. About 35 percent of the urban population had some form of municipal water service: 23 percent of these were provided with private connections, although inadequate (not sufficiently treated, low pressure, marginal storage, etc.) and 12 percent were served by public taps. The remaining 65 percent derived their water from waterways, irrigation canals and private wells. None of the population received an adequate service, of continuous supply, properly treated and disinfected.

Only 7 percent were directly connected to sewers. 65 percent were served

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Water supply

by open drains, and 23 percent had no known sewerage service.

The studies mentioned show that in developing countries the residential water supply is far from adequate, suggesting that an improved supply (quantitatively as well as qualitatively) would undoubtedly bring about important social and economic progress.

In industrialized countries there is generally enough water of the present standard to provide for the present demand. Thus how much is needed seems to depend on existing or desirable standards and the stage of economic development. In a study recently made in Sweden, VAV (1975) calls attention to the fact that residential need most probably will be unchanged. The reason for this is that water closets requiring less water will be installed.

Moreover, individual metering will be introduced in residential areas. The study also shows domestic water use in various countries. According to the authors, the differences between various countries are explained by differences in living standards, climate and general availability of water. The need for watering of lawns, for example, may vary much from region to region.

For the prediction of residential water needs, several models have been developed. The method applied to most of the earlier urban water studies has been ordinary least squares multiple regression analysis usually with the quantity consumed being a function of price, income and environmental determinants such as temperature and precipitation (Schelhorse et al.

1974). Primeaux and Hollman (1973) in a study of North Mississippi Municipalities obtained their best results by using eleven determinants:

xl = number of persons per residence x2 = number of bathrooms per residence x3 = number of dishwashers per residence x4 = number of clotheswashers per residence x5 = existence of a swimming pool

x6 = irrigable lawn space of residence x7 = market value of residence

x8 = average maximum temperature x9 = annual precipitation

xlO = education index

xll = price of water at mean level of consumption

The study revealed that the price of water was least significant compared with the results of other studies. One explanation of this is that individual household data were used in this study. In using average household data for the community all variation is obscured. The most significant determinant seemed to be the number of persons per residence which means that an adequate forecast of the population growth will bring about a good

estimate of the future residential demand. However, none of the remaining determinants could be excluded without reducing the fit.

Other studies have shown approximately the same results, ie, the number of persons per household and household income (or sales value of residence) being the most significant determinants, see for example Darr et al. (1975) and Schelhorse et al. (1974).

5.2.4 Public water demand and use

The public demand for water in an urban area is dependent on the structure of the area. This is due to the fact that the public demand may come from schools, hospitals, shops, restaurants, offices, parks, street cleaning, etc. Since large cities contain more official administration buildings, schools etc. than small cities, it may be expected that the public demand per person will rise with increasing size of the city.

According to Schelhorse et al. (1974), the public water demand should depend primarily on the level of expected services which in its turn is a function of per capita income. Other determinants would include the proportion of the city area devoted to public parks, and climatic factors such as temperature and precipitation. Unfortunately, however, few attempts have been made to examine statistically this water-use responsiveness.

Water supply

5.2.5 Industrial water demand

Contrary to the residential and public water demand, which is a direct demand reflecting individual or governmental needs and desires, the industrial demand is a derived demand.

Water is used as input to the production processes. Hence, the demand for water relies on an analysis of the water-using processes and on the demand for the products. (Schelhorse et al. , 1974) .

The authors mention five factors that should be considered in a water-use analysis of industries connected to the municipal supply:

Input side: 1. Existing state of technology, Output side: 2. Per capita income of the city,

3. The extent to which the city provides services to other than its own population,

4. Market access,

5. The general level of economic activity.

Kellar and Brewer (1975) give the following classification of industrial water use in the USA:

Percent

Process water 28.3 Air conditioning 3.2 Steam, electrical, cooling 12.1

Other cooling and condensing 51.6

Other cooling and condensing 51.6