Abstract
A geographic information system-based rainfall runoff model that simulate variable source area runoff using topographic features of the basin is presented. The model simulate the flow processes on daily time step basis and has four non linear stores viz. Interception store, soil moisture store, channel store and ground water store. Source area fraction is modelled as a function of antecedent soil moisture, net rainfall and pore capacity raised to the power of areal average topographic index (Λ). Source area fraction is used in conjuction with topographic index to develop linear relations for runoff, Infiltration and interflow. An exponential relation is developed for lower zone evapotranspiration and non-linear exponential relations to model macropore flow and base flow are proposed.
Highlights
Hewlett (1961a, b) put forward the variable source area concept of stream flow and storm flow mechanism. He concluded that the basin area contributing to stream flow changes with time and that the subsurface flow is the main source of base flow in vegetated basins
Topography plays an important role in runoff genration and is central to TOPMODEL
An alternative to curve number method for continuous simulation of variable source area based on concept of topographic index is proposed
Summary
Hewlett (1961a, b) put forward the variable source area concept of stream flow and storm flow mechanism. Where, uzetn = The evapotranspiration (mm), from upper soil zone lzetn = The evapotranspiration (mm) from ground water store LZC = The constant governing evapotranspiration from lower zone (parameter) aetn = Actual evapotranspiration on nth day (mm) Soil moisture storage: The proposed VSA model applies mass balance equation at each time step (i.e., daily) Soil moisture content is updated by following equation:. Macro-pore flow: The soil forming factors such as non-capillary cracks or channels within soil matrix are responsible for macro-pore flow to occur It depends upon various factors like rainfall intensity, pipe network, soil moisture condition, macro-pore size, catchment profile etc. The data regarding the pipe network, density of pipes, surface crack etc., is generally not available In absence of such data a simple non-linear macro-pore flow model is assumed as follows: lower zone evapotranspiration.
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