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The findings of numerousstudies on the responses of stream quality indicatorsto different levels of watershed development have been integrated into an impervious cover model. The focus on one development stressor, namely theimpervious cover, allows the decision makers to use the impervious cover model as a watershed planning toolto forecast stream response. In evaluating streamquality, the studies used various indicators such as pollutant loads, habitatquality, aquatic species diversity and abundance, and others. This studyaims to test the applicability of the imperviouscover model as a tool to set the threshold of catchment area developmentbased on the targeted water quality index. Themodel is represented by a linear relationship between the water quality indexas a response variable and catchment area imperviousness as an explanatoryvariable. The study area is an urbanized catchment area of a cascade-pondsystem located at the campus of Universitas Indonesia, Depok, West Java.Estimation of catchment area imperviousness is based on digital globe imageryand digitized based on identified rooftops. The water quality data to computethe water quality indices are collected from previous studies and relatedreports. The targeted water quality index is determinedbased on water use suitability referring to the Indonesian governmentregulation number 82/2001. Basedon the available data, an increasing tendency of temporal variation ofcatchment area imperviousness for each pond can be recognized, while waterquality index of each pond tends to decrease over time. In accordance with landcover distribution, spatial tendency indicates that imperviousness isdecreasing in downstream direction, while water quality index is increasing indownstream direction, in line with the characteristics of cascade ponds. Theresults demonstrate that despite the fact that the available data are verylimited, it is possible to use the linear relationship between catchment areaimperviousness and water quality index as a tool to set the threshold forfuture development on the catchment area of the cascade-pond system at thecampus of Universitas Indonesia with a minimum water quality index suitablejust for recreation activities. |
