Assessment of Water Resources in Northern Algeria
In Algeria, water has a strategic place in economic development, because of its scarcity and a perturbed, non-equilibrated natural cycle. Because of the limited water resources, and the need to meet the demands for the desired quantity and quality of water by the year 2010, planners must develop reasonable alternatives that take into account multiple purposes and objectives. In addition to the growing demography, 60% of the population resides in the northern range of Algeria, which represents one tenth of the total area of the country. Furthermore, inadequate water treatment due to a lack of appropriate technology, siltation of existing dams and limited capacities for water storage hamper the decision-making process. The projected data for year 2010 show structural difficulties and organizational inadequacies that are linked to the multiple operating structures in charge of collecting and conveying the information. The other major difficulty is based on the quality of the information (e.g., empirical methods and a lack of data). For example, the evaporation rate is estimated by the traditional method of a Colorado pan in which the data are mostly discontinuous. The reservoir silt load is evaluated by irregular bathymetric measurements and the results are extrapolated over a year, sometimes from one year to the next. The volume of water losses during water transport and distribution is evaluated for only a very small portion of the network and is then generalized to the entire drinking water and irrigation system. The eleven watersheds of northern Algeria encompass an area of about 130,000 km2 and offer a surface water potential of approximately 11×109 cubic meters (m3) in which only 2.13×109 m3 were collected by 98 functional dams in 1995. According to the forecasts made in 1995, the creation of new reservoirs (17 dams are actually under construction, 25 are about to start construction, and 810 sites for small reservoirs are in the study phase) will increase the mobilized volume of water to about 5.89×109 m3. The silt load for 1995 as estimated by the National Dams Agency (ANB) for all the operational reservoirs corresponded to about 0.02×109 m3. Watershed erosion and the rapid degradation of the forest cover will raise this silt load to 0.482×109 m3. This situation is very alarming for the water resources and consequently in December 2001, the exploitation of major dams (Keddara, Fergoug, Oued Fodda, Ghrib, Beni Amrane, Ksob, Foum el Gherza, Foum el Gueiss) was temporary interrupted. Operations at the Ain Dalia and Hamman Grouz reservoirs were also interrupted in October 2002 due to silt load problems. The water losses from the distribution network, which were estimated around 1.193×109 m3 in 1995, will be reduced to about 0.532×109 m3 in the year 2010 by special renovation programs. The volume of water lost by evaporation represented 0.427×109 m3 in 1995 and will double for year 2010 to reach 0.883×109 m3, according to the ANB. In 1995, groundwater was pumped at a volume of about 0.849×109 m3 from an estimated total reserve of 1.256×109 m3. The urgent program of installing an additional 2000 wells will raise the extracted volume to 1.180×109 m3 by the year 2010. In the northern portion of the country, the water needs will evolve in the following manner : · from 0.791×109 to 1.524×109 m3 per year for drinking water ; · from 1.216×109 to 7.630×109 m3 per year for agricultural needs ; · from 0.120×109 to 0.230×109 m3 per year for industry. It seems clear that the forecast made in 1995 is infeasible and unrealistic. This prediction overevaluates the financial and technical capacities to carry out all the planned projects and also overestimates the land surface for the agricultural development program. The state of water resources and their distribution for the year 2002 already indicate depletion. Accordingly, the following incentive plans were proposed : · Urgent programs for providing potable drinking water from treated seawater for coastal big cities (Algers, Oran, Arzew, and Annaba). This alternative has been implemented starting September 2002 for Annaba and Arzew. · Encouraging and developing agricultural crops that consume less water and encouraging use of modern techniques for irrigation (drop irrigation). · Activating the construction of the 800 planned watershed reservoirs. · Implementing a program for treating and recycling waste waters. The groundwater quality analysis in the northern portion of Algeria, based on the nitrate and chloride concentrations, led to the following conclusion : · Increasing nitrate concentrations for groundwater samples (up to 175 mg×L-1 for Chlef, 200mg×L-1 for Sidi Bel Abbes, and values exceeding the permissible level of 45 mg×L-1 for over half of the sampling points throughout the Mitidja). · The dilution effect during flood events does not overcome the contamination of groundwater by the nitrates. · Most of the coastal aquifers are contaminated by seawater intrusion. The chloride concentration values are about 3,650 mg×L-1 for Algiers region (Mazafran) and sometimes exceed 4,000 mg×L-1 in the eastern portion of the country (Bourchaid, Kissir). · Water samples from dams and large reservoirs were not contaminated by nitrates because of the absence of agricultural activities in the watershed. The degraded water quality and its scarcity complicate the problem of water supply that is already critical in the region. In conclusion, the gap between water needs and the available water resource is very difficult to close. The goal of this article is to review some of the effects of water shortage and its components. The present article emphasizes the need to implement a change in the decision-making process for controlling and managing water. Improved management of water supplies must not only take into account the available water but also has to optimize and rationalize its use. An urgent planning program should also be developed for treating and recycling waste water and for protecting the environment.