1.1.1.WATER RESOURCES Three main drainage systems can be distinguished: -The Mereb-Gash and Tekeze-Setit River systems, draining into the Nile River; -The eastern escarpment and the Barka-Anseba River systems, draining into the Red Sea; -The river systems of a narrow strip of land along the southeastern border with Ethiopia, draining into the closed Danakil Basin. Although no measurement of runoff is available, the internally produced renewable water resources are estimated at around 2.8km³/yr, most of which are located in the western part of the country. There is only one perennial river, the Setit River, which also forms the border with Ethiopia. All other rivers are seasonal and contain water only after rainfall and are dry for the rest of the year. There are no natural fresh surface water bodies in the country. Artificially dammed water bodies are found here and there in the highland parts of the country. Groundwater can be tapped in all parts of the country but not in the quantities and of the qualities desired. Four hydro-geological units, based on the different geological units, recharge conditions and hydraulic characteristics, can be detailed: -Granular aquifers, which cover large areas in the western and eastern lowlands and along river valleys and flood plains. Unconsolidated aquifers consisting of the alluvial and colluvial sediments are also found in the Asmara area, Red Sea coastal plains and at the foot of fault scraps and mountains; -Fissured and jointed volcanic aquifers, which are found in the central highland plateau southeast of Asmara and west of Assab, the Alid hot spring and in the southern part of the country; -Fissured and karstic aquifers of consolidated sedimentary rocks, limestone, coral reefs, evaporate deposits and the marbles of metamorphic assemblages; -Fissured aquifers of the basement rocks of crystalline metamorphic rocks and associated intrusive rocks, which are localized along weathered and fractured zones, with limited groundwater resources. The recent inventory counts 5,365 water points. About 3,374 are unprotected dug wells and 1,233 are contaminated surface water points. Typical borehole depths are in the range of 20 to 70m. Deep aquifers are not known. Problems of groundwater depletion have been reported in various parts of the country. Apparently there are a few natural springs, but an inventory is not available. Currently there are about 187 dams with a capacity of over 50,000m3 each. About 42 per cent are for municipal use and irrigation, 40 per cent for municipalities only, 13 per cent for irrigation, and 5 per cent are not used. The total capacity reaches 94 million m3. Eritrea is not well endowed with fresh ground and surface water resources owing to the arid climate prevailing in the country and due to the shortage in amount and the erratic nature of the rainfall. Eritrea has five main drainage basins, namely the Mereb-Gash, the Setit, the BarkaAnseba, the Red Sea and the enclosed Danakil basins (Mehari Haile, A., 2007). All these rivers (except the Setit River) are ephemeral, and flow during the rainy season from July to September (Mehari Haile, A., 2007). The Mereb-Gash, the Barka-Anseba and the Setit rivers all flow into the Western Lowlands, and discharge towards the eastern Sudanese plains. The MerebGash is a narrow westward oriented basin covering the area from the southern part of the central Highlands to the Sudanese border. The Setit River has perennial flows along the southwestern zone, which shares a common border with Ethiopia (Mehari Haile, A., 2007). The Barka-Anseba river originate from the northwestern slopes of the central highlands and flow northward to a confluence close to the Sudan border in the extreme Northwest of Eritrea. Although the annual rainfall volume of the Anseba-Barka basin is estimated at 14,815 million m3, the annual flow volume is projected at only 41 million m3. This is probably because much of the flow is rapidly infiltrated into the very coarse sandy plains of the river valleys and most of it is evaporated (FAO, 1994). As to the groundwater potential, no systematic investigation has been carried out and evaluations have been principally based on interpretations of aerial photography, satellite imagery and on geological maps. A large number of boreholes have been drilled throughout the country for domestic water supplies, but systematic logging has not been carried out and yields have only been estimated and not measured (Mehari Haile, A., 2007). The most important group of aquifers are the unconsolidated deposits of alluvial (Qa) or colluvial/alluvial (Qc) origin, which are unconfined with intergranular permeability. The depth to groundwater in these aquifers ranges from less than 10m to more than 150 m. Due to their heterogeneous nature, they have varying development potential, with transmissivity ranging from 100 to 3,000m2•d-1. Water quality is generally fair to good, but deteriorates significantly with salinity increasing with depth, distance from river channels and approaching the coast (Mehari Haile, A., 2007). The alluvial deposits of the main river channels offer significant potential for irrigation from the shallow groundwater, which is presently being exploited. Similarly, the colluvial sediments, which have been mapped as covering much of the Mansura and Agordat plains in the Western Lowlands, appear from satellite images to consist mainly of sheet wash/residual soils, which can be of limited thickness (FAO, 1994).

1.1.2.WATER USE Country Overview - Eritrea Groundwater is the basis of municipal water supply. Total water withdrawal was estimated at 582 million m3 in 2004, of which 550 million m3 was for agriculture (94.5 per cent), 31 million m3 for municipal consumption (5.3 per cent) and 1 million m3 for industry (0.2 per cent). The quantity of municipal wastewater can be estimated at 50,000m³/day. Treatment of municipal and industrial effluents has not yet begun. Eritrea is located in the Sahelian zone of Africa, which is not endowed with fresh water resources. In Eritrea, rainfall is the major source of water for agriculture, which is as yet underexploited. The erratic nature of rainfall (amount, distribution and intensity) is not only the primary cause for low productivity of agriculture in Eritrea. Even in good rainfall years (400-500mm in the highlands), Eritrea could only satisfy about 50 per cent of its national food requirements. It is, therefore, not only the characteristics of rainfall per se but rather the inefficient rainwater management systems that contribute most significantly to low production. In other words, due to failure to harness, conserve, and properly utilise the rainfall, agricultural droughts and food insecurity are not uncommon in Eritrea (IMAWESA, 2007). In Eritrea, a dry spell in the crop-growing season is not uncommon from late August to early September. This period lies towards the end of crop development stage and beginning of crop maturity in which crops need water for flowering and seed formation. The Eritrean farmers often say, “because of not getting one rain, we lose our crop yield”. Hence, supplying water to rainfed crops via irrigation during this critical stage is essential to mitigate the effects of dry spells so that rainwater productivity and profitability is enhanced. Supplemental irrigation in smallholder farmer systems can be achieved with water harvesting systems that collect local surface runoff (sheet, rill, gully flow) in small storage structures (IMAWESA, 2007). Estimates of irrigation potential vary from 1,070km2 to 5,670km2, the latter not taking into account the water availability. Based on water availability, it can be estimated at 1,875km2. The total land area developed for irrigation is about 220km2, while 125km2 is cultivated for producing a variety of high value agricultural crops including fruits, vegetables and cotton. The potential of spate irrigation is estimated in the order of 900km2, but the area equipped for spate irrigation covers 174km2, of which 156.5km2 are in the eastern lowlands and 18.4km2 at Alighider on the lower Gash and a small area along the Barka. The traditional technique of spate irrigation depends on the diversion of floods, a resource that is available at irregular and unpredictable intervals. The contribution of the spate irrigation to total crop production can be increased by efficient water management systems (SWE, 2008). As reported by the Ministry of Agriculture, in 2006 an estimated 168km2 were under perennial irrigation from dams, springs and wells irrigating mainly fruit, vegetables and cotton. Of the total under perennial irrigation about 1,000 is irrigated by pressurized techniques, mainly drip irrigation. In general the recent trend shows that irrigated lands throughout the country have been significantly increased during the last 15 years. In the highlands small scale community irrigation downstream of existing small dams and well use have expanded due to government and partners’ project interventions. The area under spate irrigation covered 5,197km2 (as calculated by data from the Regional offices) (SWE, 2008). In general, although the cost of running a hydro power plant is very low, they are however more capital intensive than the thermal power generation systems common in Eritrea. Currently, therefore, electricity generation is restricted to thermal plants. The country generates 60MW using diesel-fired power generation. Electricity is only available in larger cities and towns, leaving about 80 per cent of the Eritrean population without access to electricity. Some smaller villages have community diesel generators which can provide small amounts of electricity to households. Photovoltaic (PV) electricity generation is being used in special applications throughout the country (SWE, 2008).

1.2.WATER QUALITY, ECOSYSTEMS AND HUMAN HEALTH Salinity problems are present in most aquifers in the coastal areas. Generally, the salinity levels increase with the distance from the recharge area (the foothills of the eastern escarpment) and seawater intrusion has reportedly been observed up to about 20km inland. Several saline geothermal springs are present along the eastern escarpment. Salinity is also common in the northwestern lowlands. Fluoride concentrations exceeding international limits have been found mainly in the Anseba region and are probably related to the presence of certain rock types. Bacteriological contamination is very common as many water points are not protected or are not at a sufficient distance from sources of pollution. Between 40 and 90 per cent of the water sources analysed during the Rural Water Point National Inventory have been found to be biologically contaminated in the various regions. Pollution problems are basically related to municipal sewage. A large part of the groundwater in the Asmara area has a very high nitrate content, which is due to the effects of the many latrines located in the town. Industrial pollution as well as irrigation-related pollution is not yet a problem because of the limited activities of the two sectors. Malaria incidence and prevalence are increasing. Malaria affects about 67 per cent of the population and forms about 30 per cent of total outpatient morbidity. It is the major cause of morbidity and mortality of women and children. P.falciparum is the cause of 94 per cent of all cases of malaria.

(Water Risk Filter)