The report deals with the hydrological aspects of watershed development and describes watershed components and watershed models. It gives an account of the various watershed models in details including data requirement, input, output, various physical processes and governing equation. The suitability of a particular model to Indian condition is also highlighted in the report.
It begins with an introduction on watershed and discusses the need for watershed development, hydrology of small watersheds and soil & water conservation measures. It then goes on to discuss in details the import of various aspects of watershed such as watershed characteristics, components, size, shape and linear & relief aspects of the drainage network.
Other watershed parameters such as precipitation, interception, surface retention, surface detention, infiltration, evapotranspiration, soil moisture, streamflow, baseflow, erosion and sediment yield are also discussed.
The study thereafter explains the diverse models available to simulate the complex hydrological processes. These models have different approaches and methods of approximation of each hydrological process. The models discussed include –
- LISEM: A physically based model provides improved process description for infiltration and detachment.
- WEPP: A continuous model simulation computer programme, which predicts spatial and temporal distribution of soil loss and depositions in a watershed.
- TOPMODEL: It is a set of conceptual tools to reproduce the hydrological behavior of catchments in a distributed or semi-distributed way, in particular the dynamics of surface or sub-surface contributing areas.
- SHE: It is a practical system for simulating land use change, groundwater and soil moisture conditions, spatial variability in catchments and water flows controlling the movements of pollutants & sediments for ungauged basins.
- USLE: It is used for predicting overland flow, sheet rill erosion and provides more complete separation of factors effect.
- EPIC: A field-scale model that simulates hydrology, erosion-sediment, nutrient, nutrient-cycling, plant growth, aluminium toxicity/ lime, soil temperature, tillage, economics and plant environmental control.
- SWAT: It is designed for biophysical processes and can explore alternative watershed management options.
- SWMHMS: It is used as an educational tool for students learning the principles of hydrologic modeling.
- AGNPS: It is a distributed grid model with model parameters for each grid and is used for simulating a single storm event.
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