Development of a basin management program to improve water quality in rivers based on an environmental water quality predictive model

Abstract This research has the aim of establishing the amount of land that the Conservation Area National System (SINAC) needs to buy and specifying its use inside the Golfo Dulce Forest Reserve in order to maintain the good quality of the rivers. The study was done inside Rincon sub-basin in the Osa Peninsula, a land dedicated to primary and secondary forest (Melina tree plantations), mangrove forest, urbanism, chaparral, pasture for grazing livestock and crop cultivation, mainly rice and African palm; uses that may change in time affecting the actual water quality (WQ) in rivers and the bay. Changes in land uses modify the WQ and it can be predicted using WQ models based on environmental variables through the evaluation of different scenarios. It was found through modeling that pasture or chaparral land use has no negative impact on WQ; all the contrary happens with increments in crop cultivation or human population. At the present, the coastal area, adjacent to the reserve, has low agricultural activity but that could increase over time, affecting the WQ. Therefore, SINAC should continue with its acquisition land activity to counteract the negative environmental effect of agricultural activity to preserve the actual good quality of the rivers.