1.1.1.WATER RESOURCES The water resources of El Salvador are estimated at 17.8km3, of which 11.6km3 are from surface water. 84 per cent of this runoff occurs during the rainy season and 16 per cent during the dry season. El Salvador is the only Central American country whose territory drains entirely into the Pacific Ocean. The country has about 360 rivers, which together form 10 hydrographic regions. There are a few surface water contributions from Honduras and Guatemala, estimated at 7.5km3 per year. In this regard, only the Paz River (which forms the boundary with Guatemala) has a use agreement with bordering countries. The groundwater recharge through infiltration is estimated at 6.15km3. From this volume 5.97km3 are considered passing base flow recharge surface water courses and, therefore, with the possibility of extraction; the remainder represents direct discharge of coastal aquifers to the sea. The best aquifers are located in the coastal zone and in the valleys of the central plateau. There are four lakes in El Salvador (Llopango, 70.1km2; Guija, 44.1km2, Coatepeque, 24.8km2; and Olomega, 24.2km2), and four hydroelectric dams: (Reservoir 5 de Novembre, 20km2; Cerron Grande Reservoir, 135km2; Reservoir 15 de Septiembre, 35km2; and Guajoyo). The total installed capacity of power generation is 943.4MW, of which 388MW (41 per cent) are generated by four hydroelectric plants. The country's hydroelectric potential is estimated at 1,889MW, accounting for 1,409MW to the Rio Lempa, which currently uses only 21 per cent of the total it could use. Hydro generation in 1997 was 2,623GWh (24 per cent less than the year before as a result of damage to power systems because of weather) and total energy demand is 3,636 GWh. 1.1.2.WATER USE The latest data on total annual water extraction are from 1992, with a value of 729 million m3, with the aquifers of the Lempa River basin being the leading suppliers. With regard to drinking water extraction, the information available is from 1997: 262.3 million m3 (the value in 1992 was 246 million m3). In fact, 158.9 million m3 (61 per cent) were extracted from the aquifer in the San Salvador metropolitan area which already has excessive levels of exploitation. Drinking water coverage in 1997 was 53 per cent of the total population. That same year global sanitation coverage was 66 per cent (59 per cent connected to the sewerage system and 22 per cent of latrines in urban areas and 51 per cent of latrines in rural areas).

1.2.WATER QUALITY, ECOSYSTEMS AND HUMAN HEALTH The pressure on El Salvador's natural resources is very high, which is causing a great decrease of forest area (6.1 per cent of its coverage in 1992 and 2 per cent in 1997), and causing changes in the regulatory capacity of the hydrological cycle. Erosion (6.6mm/year in 75 per cent of the country) has significantly increased sediment transport in rivers; for example, the Lempa River carries an estimated 10 to 25 million tons per year. Furthermore, the fact that wastewater sewer systems do not receive any treatment before being discharged to the rivers has degraded more than 90 per cent of the rivers, exceeding the threshold levels of biochemical oxygen demand. This situation is increased in the rivers Acelhuate, Suquiapa, Sucio and Quezalapa, affecting the Cerrón Grande reservoir as well as other coastal ecosystems.