A dynamic model for predicting hydrologic response to land cover changes in gauged and ungauged catchments

The potential impacts of deforestation on hydrological response are of significant importance in highland regions of northern Thailand and other parts of southern Asia. In these regions, where climate exhibits strong seasonality, the availability of water in the dry season determines the feasibility of multiple crop rotations. Based on the IHACRES rainfall-runoff model, a simple scaling procedure and landcover data, this paper presents a simple hydrologic approach to predict hydrologic response to land use changes, and to predict streamflow in ungauged catchments. The latter is a major hurdle in water resource analyses in regions like northern Thailand where there is a lack of stream gauge instrumentation, or where assessment of water availability is required at locations between gauging sites as input to agricultural production models. A simple regionalisation of streamflow response was tested for three gauged subcatchments of the Mae Chaem catchment in northern Thailand. Overall performance was superior when calibrated parameters from the largest catchment were used to infer parameters for the regionalisation. Most importantly, the procedure was able to predict the relative pattern of annual and seasonal flows, whatever the reference catchment on which the regionalisation was based. Investigations of the impacts of forest cover changes on modelled hydrological response are presented and the key model parameters to which model outputs are most sensitive are discussed.