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Modelling a catchment and study site in Andhra Pradesh by applying a rainfall – runoff model developed for West Bengal

Wilmink, R.J.A. (2013) Modelling a catchment and study site in Andhra Pradesh by applying a rainfall – runoff model developed for West Bengal.

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Abstract:In Andhra Pradesh (state of India) watershed development programs (WSD) have been undertaken to improve the livelihood of farmers. Most farmers in India are poorly educated, have bad healthcare and only have small landholdings. The cropping for these farmers is therefore very difficult, which is reinforced by the shift in timing of the monsoon, the increased dry spells and the population growth. Andhra Pradesh has a semi-arid climate, with an average yearly rainfall of 450 – 600 mm, falling mostly between July and October. Hydrologically, the catchment area of Andhra Pradesh consists of uplands (‘’Tarh’’, not suitable for cropping), medium uplands (only suitable for cropping when terraced and bunded, then called ‘’Baidh’’), and lowlands (suitable for cropping). The population growth is forcing farmers to crop outside the lowlands, shifting to the medium uplands, which are much dryer. The terms Tarh and Baidh are used in a previous WSD study in West Bengal. Due to the different languages used in India, these terms are likely to be different from the terms used in Andhra Pradesh. However, for consistency, these terms will be used for the catchment modelling in Andhra Pradesh too. This bachelor thesis is a small part in a WSD study into the effects of WSD policies in relation to the investments level of return on the meso-scale. The purpose of this research is to: ‘’Apply the model developed for the West Bengal study site to the study sites for a second project in Andhra Pradesh (India), extending the application to a larger scale.’’ The research started with the original model developed for West Bengal by Groeneveld (2012). After a data analysis, which gave information about the input data, the individual rainfall gauges are chosen as the rainfall input data to continue this research. The original model has been modified based on performance indicators and a visual interpretation of a gauged catchment area (~2750 km2) to create a model that generates a better representation of the catchment’s hydrology. This modification included a change in model structure as well as in the model processes. Finally this model has been applied to an ungauged study site (~200 km2). The modified structure and processes represented in the model, based on visual interpretations of the catchment and study site using Google Earth, and applying a simple approach of new model processes, gave a better representation of the catchment’s hydrology than the original model. The Nash-Sutcliffe coefficient and Relative Volume Error of the generated runoff by the model over the period of study are 0.66 and -15.8 % respectively. The underestimation by the model was expected and could be justified. Because of a lack of good quality, high resolution and high frequency data, only indications about possible problems with the data could be made where a mismatch of the modelled and measured runoff occurred. Also, scarce information of the catchment’s area characteristics led to many assumptions, mostly derived from related studies. However, several possible data problems could be identified. These identified issues were able to clarify some observed errors in the data. This all resulted in recommendations and additional research themes about the data, model processes and area characteristics. Applying the modified calibrated version of the model on the ungauged Gooty study site required a visual inspection of the study site, which led to a small change in model structure. The rainfall-runoff coefficients of the gauged and ungauged areas gave comparable results. The difference in modelled rainfall-runoff coefficients could mostly be related to the change of input data between the gauged catchment and the ungauged study site. Finally, the model developed in this research has approved capability of modelling the catchment and study site in Andhra Pradesh. These model codes (the code for the catchment and the slightly different code for the study site) can be used for estimating, and possibly measuring, the effects watershed developments in this region of India, trying to improve the livelihood of farmers.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
Link to this item:http://purl.utwente.nl/essays/64309
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