Map of study area/sampling sites in the landscape. Inset view simulates the complete 2510 km stretch of river Ganga from Himalaya to Bay of Bengal. Abbreviations: S#1, site 1: Bithoor (most upstream site); S#2, site 2: Bhairon ghat; S#3, site 3: Parmat ghat; S#4, site 4: sattichaura ghat or nana-rao ghat; S#5, site 5: jajmau (most downstream site). Arrows indicate the direction of surface water flow in the up-to-down-gradient fashion in the landscape. Topographic data based upon Survey of India map (adopted from http://www.ttkmaps.com).