for one concrete dam (Al Heffeh). They are mostly built for irrigation, some also provide domestic water or generate electricity.
The few exceptions are as follows:
- Tabqa (Euphrates): Irrigation (64,000 ha) and electricity (2500 GWh/year).
- Ba’ath (Euphrates): Electricity (375 GWh/year) and Tabqa re-regulating dam.
- Rastan (Orontes): Irrigation (72,000 ha with Mehardeh) and electricity (57 GWh/year).
- Mehardeh (Orontes): Irrigation and electricity (18 GWh/
year).
- Jabal Al Arab (Yarmouk): Domestic water supply.
Wadi Hydrology: Process Response and Management Implications
The Ministry of Irrigation is responsible, at the national level, for the construction, operation and maintenance of the national stations (which measure surface and subsurface water levels) as well as for processing, publication and analysis of the obtained data. Besides the national networks, most of the water basins have their own hydrometric stations.
The following basic parameters are measured at the national stations: water level, current velocity, water discharge, water temperature, electric conductivity of water, pH, dissolved oxygen content, and a number of chemical parameters.
At present, the Ministry of Irrigation is responsible for the operation of hundreds of stations for surface water level measurements and tens of stations for groundwater measurements. Water discharges are measured at hundreds
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Figure 4. Rate of construction of dams.
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:I 8. 8. - Table of Basin
+ ++ International boundary
- River
0 City
A Basin N?
l Dam with capacity f hm
-.- Basin boundary
1 Dam N?
Figure 5. Important reservoirs in Syria.
of gauging sites. On the other hand, there are many other stations in different Governorates for water level measurements, water discharge measurements, and precipitation measurements within the responsibility of other Agencies and Directorates (e.g. Ministry of Agriculture, General Directorate of Climatology). In some places, real- time control of the water resources requires direct and immediate measurements of water levels, and discharge (e.g.
for reliable runoff forecast).
Since 1970, within the frame work of the National Program of the analytical study of rivers in Syria, the following parameters have been measured at several stations of the National Hydrometric network: Alkalinity, Calcium, Magnesium, Total Hardness, Nitrites, Nitrates, Ammonium, Nitrogen, Chlorides, Sulphates, Sodium, Potassium, Total Organic Carbon Content, Dissolved Organic Carbon, Zinc, Copper, Lead, Cadmium and Mercury.
Directorates of Water Resources Pollution Control provide the specialists, engaged in water resources protection, with the basic data on the physical and chemical characteristics of water in the rivers of Syria. The Ministry of Irrigation, Directorates, individuals, and Research Institutes and
Centers make their studies on several water basins; out of which eight basins are under the responsibility of the Ministry. Additional stations are operated by other bodies (Ministry of Agriculture, General Directorate of Climatology, Water Research Center, Center of the Research and Scientific Studies, etc.). Their activities include:
determination of long-term fluctuations of water discharges, compilation of water balances, evaluation of sediment discharge in particular regions, and preparation of basic documents for regional training and research.
Before 1970, only quantitative aspects of water were observed. Water quality problems were recognized later, which led to the establishment of additional stations for solid discharge measurements, water temperature measurements, and chemical parameter measurements.
6.1 Network design and administration
At present, quite reliable information on water levels and discharges are available in Syria. This information has been collected for a long period of time. The purpose of the network design is to make a critical assessment for stations operation. Recent analysis indicated that most of the stations are needed for water management (operation of hydraulic 140 Proceedings
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the UNESCO / NWZC / ACSAD Work& o p J ON “Wadi Hydrology ‘* and “Groundwater Protection ”Wadi Hydrolqy: Process Rapome and Management Implications
structures, runoff control, design, development of projects in water management, etc.), environmental protection (protection against water pollution and depletion), and national water resources inventory. They also indicated a great need for data on extreme discharges.
Stations for water discharge measurements were mainly installed on the largest rivers. The inadequacy of data concerns mainly small and mid-sized rivers, with drainage areas from 1 km2 to 120 km2. Discharge can also be evaluated through indirect methods. Current information for small watersheds is insufficient for verification and evaluation of extreme discharge events.
On the other hand, the analysis of the existing data, and application of statistical methods (e.g. regression methods), makes it sometimes possible to translate the results of measurements to other sites. It may be possible to close few stations in some specific locations.
The General Directorates in the Ministry of Irrigation are responsible for the following activities.
Planning construction, maintenance and operation of hydrometric stations (measuring networks);
Hydrological data delivery in the appropriate form;
Collection, control, primary processing, classification, and storage of hydrological data;
Training of the personnel;
Coordination of hydrological observations and data processing between Governorates in the form of methodological instruction;
Preparation of reports and studying the water resources for large river basins, as well as making long-range forecasting for the development of these basins, in particular, concerning water levels, discharges, water temperature and sediment transport;
Preparation and transmission of hydrological forecasts on water levels and discharges, as well as forecasts of the transport of pollutants into the Euphrates, Orontes, Yarmouk and other important rivers;
Publication of the hydrological year-books for each basin and for the whole country.
6.2 Instruments and methods of observation
For water level measurement, the General Directorates in the Ministry of Irrigation apply staff-gauges, water level recorder with floats, and pneumatic water level recorders.
Also, pressure sensors have been recently introduced into practice. Water discharges are measured quite reliably during flood at permanent gauging sites in streams, where runoff conditions are optimum and solid discharge is limited. Such conditions are seldom observed in Syria.
Accurate discharge measurements during floods are often impossible with the current meters because of the high speed
of bed load, suspended sediment transport, river bed deformation during floods, and rapid water level fluctuations,...etc. New technologies would produce more accurate measurements, but still many difficulties exist.
For operational measurements of suspended sediments, a bathometer for water sampling is fixed to a rod or suspended from a cable. This bathometer takes water samples from the water surface, as well as from various depths.
Solid sediments are measured by ordinary or automatic thermographs. Stations for water quality measurement are equipped with instruments for manual or automatic water sampling, for continuous measurements of some parameters.
6.3 Observing program
Limnigraphic diagrams, where water levels are recorded, are replaced every few weeks. Hydrometric stations deliver data on water levels, measured for the previous 12 hours or more. A new generation of automatic devices for: water level measurements, discharge measurements, temperature, electric conductivity, Oxygen content, pH...etc. will be fixed to most water basins of Syria.
Water samples, intended for suspended sediment measurements or other chemical analysis, are taken in bottles to the laboratories of the Ministry of Irrigation.
Special teams are engaged in the construction, operation and maintenance of the stations.
6.4 Data collection processing and storage
Data are first checked for gaps (gaps are filled by probable values), and for the coincidence of the control measurements taken at local site (in situ). The data are also checked for likelihood, taking into account the characteristics of other stations, and measurements at adjacent sites.
Then, the data are transformed into digital form (the rating curve of the station is also included). Tables and preliminary graphs are consequently developed. At this stage, it is possible to correct the transformed values.
Some data are delivered to the Hydrological Data Bank in the Ministry Headquarters. At this stage, the Hydrological Year-Book of Syria is produced.
6.5 Effectiveness of the network
During the recent years, the Ministry of Irrigation of Syria made efforts to define the demands of other administration and research institutes. These attempts were made for adapting the existing network to data needs.
Studies show that the stations available on the large streams are quite sufficient, for discharge measurements and for water quality determination. On the other hand, the number of stations on the small streams is quite insufficient.
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As to sediment discharge measurements, the number of measuring should be increased, the objectives of the network up-dated. For network optimization, many parameters are considered, of which major ones are costs for maintenance of the station, operational costs, practical importance of the measured data, preliminary investment, obligatory payment, contribution of other organizations, required accuracy, possibility of getting the required information at the required accuracy by means of computing the results of measurements, and cost-benefit analysis.