ADB_book_18 April.qxp - Himalayan Document Centre - icimod

to intense weathering, and percolation rates havedecreased. The Siwalik watershed areas are nowimpoverished and water recharge into the soil hasbeen reduced. During the rainy season, the heavyrainfall coupled with the soft rock results inmaximum sediment loads to rivers and streams. Adecline in the level of the groundwater table hasbeen reported, and desertification has begun in theTerai due to deforestation in the Siwalik range. In theSiwalik area of eastern Nepal, forest coveragedeclined by nearly 13% between 1979 and 1999, and68 ha of land was damaged as a result of landslides(IUCN 2000).Use of Water ResourcesTable 5.2 shows the water availability and use bysectors in 1995 and 2001. The country has about 224km 3 of annual renewable water, and the annual percapita water supply in 2001 was 9,600 m 3 , down from11,000 m 3 in 1995 (DHM 2001). In 1995, the totalannual withdrawal of water for consumptive uses(domestic, agriculture, and industry) was 14 km 3 andper capita annual withdrawal of water was 690 m 3 .Although the total annual withdrawal of waterincreased in 2001, most of the increase went toagriculture, while the percentage used for domesticpurposes decreased (UNEP 2001). Agriculture usedabout 96% of the total withdrawal in 2001, mostly forirrigation, with the domestic sector’s share less than4%. The use of water by the industrial sector isinsignificant. The estimated total annual waterrequirement for irrigation in the cultivated area is 67km 3 , which makes up nearly 30% of the total waterpotential of 224 km 3 .Current annual withdrawal of groundwater isabout 0.756 km 3 for irrigation and 0.297 km 3 fordomestic uses (WECS 2004). Groundwater is thebest alternative source of water supply, particularly inthe Terai region and Kathmandu Valley. The totalTable 5.2: Water Availability and Use by Sectors, NepalDescription 1995 a 2001 bTotal annual renewable water resource(km 3 /year)224.0 224.0Per capita renewable water resource('000 m 3 /year)11.0 9.6Total annual withdrawal (km 3 /year) 14.0 18.5Per capita annual withdrawal (' 000m 3 /year)0.69 0.8Withdrawal (percent) Domestic 3.8 3.6Industry 0.3 0.3Agriculture 95.9 96.1km 3 /year = cubic kilometer s per year, m 3 /year = cubic meters per yearNote: 1 billion m 3 = 1 km 3 .Source: a UNEP (2001); b WECS (2004)ground water potential of the country is 12 km 3 , ofwhich 5.8 to 11.5 km 3 can be extracted annuallywithout any adverse effects. However, the level ofgroundwater in Kathmandu Valley is alreadydropping due to overexploitation, as described in thenext section. The Bhabar zone with dense forestcover, a contiguous area of the Terai, is the rechargearea for the Terai’s groundwater.In addition to these uses, river water is also usedfor generating hydropower. The country has 83,000megawatts of potential hydropower generation, ofwhich 42,000 megawatts are economically viable. Atpresent, total electricity generation is around 559megawatts (WECS 2004). Further, microhydropowerplants are operated in several parts of the Hill and theMountain regions, although their contribution to totalhydropower generation remains small at 1.2%. Localstreams and rivulets are also important sources ofenergy for agro-processing in the Hill and Mountainregions. Operation of water mills (ghattas) forgrinding grain has existed for centuries; it isenvironmentally sound though not veryeconomically profitable. There are about 25,000water mills in Nepal (MOPE/REDP 2002).Sources, Quantity, and Quality ofDrinking WaterThe quantity and quality of water directly andindirectly affect human activity, health, andsanitation. These in turn depend on the watersources. Normally a person requires two liters ofwater per day for basic physiological processes(WHO 1996). Water quality refers to the suitability ofwater to sustain living organisms. For humans, it isused for drinking, bathing, washing, irrigation, andindustry. Changes in water quality are reflected in itsphysical, biological, and chemical conditions, andthese in turn are influenced by natural andanthropogenic activities.Sources of Drinking WaterNepal is a mountainous country with diversephysiographic regions, and thus different sources ofdrinking water are available for people in differentareas (Table 5.3). Tap water is the most importantsource, providing drinking water to almost 53% of allhouseholds. Tap water refers to water piped directlyfrom a source as well as to centrally distributed andpretreated water. The second most important sourceis tube wells. These two sources are important inboth urban and rural areas. The relative share of tapwater in urban and rural areas is 65% and 51%,respectively, followed by tube wells with 23% and56 Environment Assessment of Nepal : Emerging Issues and Challenges