Assessing hydrologic response to climate change of a stream watershed using SLURP hydrological model

The impact on streamflow and groundwater recharge considering future potential climate and land use changes was assessed using Semi-distributed Land-Use Runoff Process (SLURP) continuous hydrologic model. The model was calibrated and verified using 4 years (1999–2002) daily observed streamflow data for a 260.4 km2 watershed which has been continuously urbanized during the past couple of decades. The model was calibrated and validated with 0.72 average coefficient of determination and 0.69 average Nash-Sutcliffe model efficiency respectively. For the future climate change assessment, three GCMs (MIROC3.2hires, ECHAM5-OM, and HadCM3) of IPCC A2, A1B, and B1 scenarios from 1977 to 2099 were adopted, and the data was corrected using 30 years (1977–2006, baseline period) ground weather data and downscaled by Change Factor simple statistical method. The future land uses were predicted by Cellular Automata-Markov technique using the time series land use data of Landsat images. The 2080 land uses showed that the forest and paddy areas decreased 10.8% and 6.2% respectively while the urban area increased 14.2%. For the future vegetation canopy prediction, a linear regression between monthly Normalized Difference Vegetation Index (NDVI) from NOAA/AVHRR images and monthly mean temperature using eight years (1997–2004) data was derived for each land use class. The 2080s highest NDVI value was 0.64 while the current highest NDVI value was 0.51. The future assessment showed that the annual streamflow increased up to 52.8% for 2080 HadCM3 A2 scenario and decreased up to 14.5% for 2020 ECHAM5-OM A1B scenario respectively. The seasonal results showed that the spring streamflow of three GCMs clearly increased while the summer streamflow decreased for MIROC3.2 hires and ECHAM5-OM, and increased for HadCM3 corresponding to each precipitation change of GCMs. The portion of future predicted Evapotranspiration (ET) about precipitation increased up to 3.0% in MIROC3.2 hires, 16.0% in ECHAM5-OM, and 20.0% in HadCM3 respectively. The future soil moisture content slightly increased compared to 2002 soil moisture. The increase of soil moisture resulted in the increase of groundwater recharge except ECHAM5-OM. The increase of summer ET gives us a decision making in advance for the security of future water demands. Thus the increased streamflow during spring period has to be managed more carefully and efficiently than the present situation.