Evaluation of Non-point Source Loads in the Reservoir Watershed using the GIS/GPS/RS Information Technologies and Numerical Models

Abstract

One of the recent concerns of reservoir eutrophication issues focuses on a fast assessment of the non-point sources pollution impact. It frequently requires an initial evaluation of the land use pattern and the reservoir assimilative capacity. This information is useful for estimating the non-point source loads, assessing the proper uses of natural resources in the watershed, and generating the essential control strategies when required. To achieve this goal, the state-of-the-art 3S information technologies, which properly integrates the skills of geographic information system (GIS), global positioning system (GPS) and remote sensing (RS), is viewed as an integrated means for reservoir land use assessment and watershed management. Substantial efforts in this study are placed upon identifying seven types of land use patterns in the watershed of the Tseng-Wen Reservoir in Southern Taiwan, which would directly assist in the required estimation of non-point sources pollution impact. With the aid of SPOT satellite images, Erdas Imagine0 image processing system, and ArcView0 GIS, the numerical model based on the export coefficient method yields an estimation of non-point source loads on a yearly basis with respect to four target constituents. These constituents of interest consist of total phosphorus (TP), total nitrogen (TN), biochemical oxygen demand (BOD), and total suspended solid (TSS). The analysis of assimilative capacity of the Tseng-Wen Reservoir based on various types of numerical models is also included for the evaluation of the eutrophication issue. Advanced management strategies with regard to the proper use of assimilative capacity of the Tseng-Wen Reservoir and the land resources in the watershed are then discussed in terms of three classified impact levels of non-point sources in the watershed. The methodology is proved practical, promising, and effective for assessing the eutrophication issue in the reservoir watershed within a short period of time