Characterization of upper konaweha watershed and testing the effect of land cover and climate change with hydrological model

Abstract

Land cover and climate conditions have an important role in supporting the hydrological function in waterhed area. Hydrological modeling approach can be used to analyze the response of hydrological functions to land cover and climate change. In this research, we used the Generic River Flow (GenRiver) Models to simulate the impact of land cover convertion and simple climate change on the water balance of the Upper Konaweha Watershed (2856 km2) that is located in Konawe and Kolaka District, Southeast Sulawesi. Later, the discharge of Upper Konaweha Watershed will lead to Pelosika Dam. The objective as well as the steps of this study were: (1) to describe the characteristics of hydrological and climate of Upper Konaweha watershed as an input of hydrological model; (2) to calibrate the GenRiver and HBV Models based on observational data, and if necessary modify the GenRiver Models, and (3) to simulate the impacts of climate and land cover change using a hydrological model. The simulation of the impact of land cover and climate change toward present hydrological condition was based on 1990-2010 data. While the future simulation scenarios for the next 21 years (2010-2030), considered 8 factorial combinations of: (1) Bussiness as usual (BAU) (extrapolatimng land cover change as occurred in the last 21 years (1990-2010)) versus no change from 2010 condition; (2) local translation of global climate scenarios AIF1 and B1 (IPCC Scenarios); and (3) high and low rainfall intensity. Upper Konaweha Watershed has annual rainfall variated between 907.1-2270.2 mm with average of potential evaporation 115.1 mm. Based on the characteristic of stream network, Upper Konaweha Watershed can be divided into nine sub-watershed. The performance evaluation results between GenRiver and HBV model showed that both models have equal performance with the difference of NSE is 0.02. While the simulation result showed the potential changes in rainfall intensity, without change in daily rainfall, would have considerable impact on surface flow and seasonal pattern of discharge. Otherwise, land cover change will have a more modest impact and climate changed on IPCC Scenario will not be expected to have a significant influence on water balance in the Upper Konaweha Watershed.