title: An appraisal of precipitation distribution in the high-altitude catchments of the Indus basin.
abstract: Scarcity of in-situ observations coupled with high orographic influences has prevented a comprehensive assessment of precipitation distribution in the high-altitude catchments of Indus basin. Available data are generally fragmented and scattered with different organizations and mostly cover the valleys. Here, we combine most of the available station data with the indirect precipitation estimates at the accumulation zones of major glaciers to analyse altitudinal dependency of precipitation in the high-altitude Indus basin. The available observations signified the importance of orography in each sub-hydrological basin but could not infer an accurate distribution of precipitation with altitude. We used Kriging with External Drift (KED) interpolation scheme with elevation as a predictor to appraise spatiotemporal distribution of mean monthly, seasonal and annual precipitation for the period of 1998-2012. The KED-based annual precipitation estimates are verified by the corresponding basin-wide observed specific runoffs, which show good agreement. In contrast to earlier studies, our estimates reveal substantially higher precipitation in most of the sub-basins indicating two distinct rainfall maxima; 1st along southern and lower most slopes of Chenab, Jhelum, Indus main and Swat basins, and 2nd around north-west corner of Shyok basin in the central Karakoram. The study demonstrated that the selected gridded precipitation products covering this region are prone to significant errors. In terms of quantitative estimates, ERA-Interim is relatively close to the observations followed by WFDEI and TRMM, while APHRODITE gives highly underestimated precipitation estimates in the study area. Basin-wide seasonal and annual correction factors introduced for each gridded dataset can be useful for lumped hydrological modelling studies, while the estimated precipitation distribution can serve as a basis for bias correction of any gridded precipitation products for the study area.
authors.affiliation: Climate Change Alternate Energy and Water Resources Institute, National Agricultural Research Centre (NARC), Pakistan Agricultural Research Council, Islamabad, Pakistan; Earth System Science, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands. Electronic address: zakir.dahri@wur.nl.
authors.forename: Zakir Hussain
authors.initials: ZH
authors.lastname: Dahri
authors.affiliation: Earth System Science, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: Fulco
authors.initials: F
authors.lastname: Ludwig
authors.affiliation: Climate Change and Adaptive Land & Water Management, Alterra Wageningen UR, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Earth and Climate Cluster, Faculty of Earth and Life Sciences. VU University Amsterdam, The Netherlands.
authors.forename: Eddy
authors.initials: E
authors.lastname: Moors
authors.affiliation: Climate Change Alternate Energy and Water Resources Institute, National Agricultural Research Centre (NARC), Pakistan Agricultural Research Council, Islamabad, Pakistan.
authors.forename: Bashir
authors.initials: B
authors.lastname: Ahmad
authors.affiliation: Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom; Department of Engineering, University of Engineering and Technology, Peshawar, Pakistan; International Institute for Applied Systems Analysis, Schlossplatz 1, A-2361 Laxenburg, Austria.
authors.forename: Asif
authors.initials: A
authors.lastname: Khan
authors.affiliation: Earth System Science, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands; International Institute for Applied Systems Analysis, Schlossplatz 1, A-2361 Laxenburg, Austria.
authors.forename: Pavel
authors.initials: P
authors.lastname: Kabat
keywords: Bias correction; Gridded precipitation products; High-altitude areas; Indus basin; Precipitation distribution