Forsythe, N., Kilsby, C.G., Fowler, H.J. and Archer, D.R. 2012. Assessment of runoff sensitivity in the Upper Indus Basin to interannual climate variability and potential change using MODIS satellite data products. Mountain Research and Development, 32(1), 16-29, DOI: http://dx.doi.org/10.1659/MRD-JOURNAL-D-11-00027.1

Abstract

The Upper Indus Basin (UIB) covers an area of more than 200,000 km2 and an elevation range from below 1000 to over 8000 metres m asl. Its water resources underpin Pakistan’s food security and energy supply. Vertical and horizontal variations in key climate variables govern the runoff contributions of the UIB’s various elevation zones and sub-catchments.Remote sensing climatic data products from NASA’s Moderate Resolution Imaging Spectrometer (MODIS) instrument platform provide an opportunity to develop a spatial characterisation of the climatology of remote and rugged regions such as the UIB. Specifically, snowcovered area (SCA) and land surface temperature (LST) have been shown to provide good analogues respectively for precipitation and air temperature. As such, SCA and LST quantify regional variations in mass and energy inputs to runoff generation processes. Although the ten year (2000-2010) MODIS observational record is not adequate to evaluate long term trends it does provide a consistent depiction of annual cycles and a preliminary assessment of interannual variability. This study presents a summary of the period means and interannual variability found in remotely-sensed SCA and LST products for the UIB. It then provides an update of locally observed recent climate trends for the 1962 to 2007 period. Non-parametric trend tests are applied both to the local observations and remote sensing records to assess patterns in recent variability. The climatic noise (intense variability) of the past decade, however, renders conclusions on nascent trends in SCA and LST premature. Finally runoff sensitivity to temperature change – spatially applied as Summer (JJA) night-time 0°C LST isotherm migration– is assessed for a range of potential scenarios. Results indicate that changes in mean Summer (JJA) runoff could range from -30% to +35% or more depending on whether recent locally observed changes continue or scenarios derived from current regional climate model (RCM) simulations unfold.