Scope of Payment for Ecosystem Services Mechanism for ... - icimod

and Perera (2005) reported that the build-up area in the valley expanded fivefold from3,330 ha in 1955 to 16,472 ha in 2000. Similarly, Haack and Rafter (2006) reported thatthe increase in the urban area between 1978 and 2000 has been over 450 percent. Apattern of urban growth in Kathmandu valley from 1955 to 2000 is shown in Figure 2.1which clearly reflects that much of the changes in the rate of urbanization have occurredbetween 1991 and 2000 (Sada, 2010).8(Source: Pradhan and Perera, 2005)Map 2.1: Land use change in the Kathmandu Valley from 1955 to 2000.The contribution of landuse changes to water pollution links through the changes in thelocal hydrology. Conversion of open land and areas under vegetation cover to buildupareas is known to increase the rates of overland flow and reduce the soil infiltration andgroundwater recharge, resulting to decline in the groundwater level. According to Metcalfand Eddy (2000), the groundwater level has dropped from 9 meters to as low as 68 m inthe valley over a few years (Sada, 2010).2.2 PES TheoryA watershed is the area of land that feeds water into a river, through the process ofprecipitation draining through the landscape, into tributaries and into the main riverchannel. Watersheds are also called „catchments‟, „drainage basins‟ or „river basins‟. Thevarious components that make up the landscape within a watershed, for example forests,