RN-37 : Hydrological aspects of droughts

Abstract

Drought forms one extreme end of the hydrologic cycle. It represents a period of abnormally dry weather sufficiently prolonged for the lack of precipitation to cause a serious hydrological imbalance and connotations of a moisture deficiency with respect to various water uses. Drought is a frequent hazard in India which causes local as well as regional imbalances and put a drag on the economy of the nation. The study of droughts is an extremely relevant and essential aspect for the overall planning and management of water resources in order to meet the increasing demand on available water for different uses in periods of distress. The studies on hydrological aspects of drought are less attempted as compared to the meteorological and agricultural aspects of drought.

The time and space variability in the hydrological process of an area is required to be studied to better analyse and understand the problem of drought. Number of deterministic , statistical and stochastic approaches are available for quantification of various aspects of hydrological drought using hydrological variables such as stream flow, reservoir storages, soil moisture and ground water. However, the inadequate data situation, somewhat restricts the use of such approaches for drought quantification.

This report focuses on the analysis procedures to study the phenomena of drought. It deals with hydrological aspect of drought and the statistical approaches for the analysis of low stream flow, which is an important hydrological variable , in order to quantify the various parameters related with drought characteristics. However, those approaches can also be extended to study the other aspects of hydrological drought using hydrological variables such as soil moisture ground water etc. with little or no modifications. The methods available for regional analysis of multiyear hydrological droughts are also discussed. Such regional relationships are very much useful to estimate the parameters of drought severity, magnitude and durations for the ungauged catchments. There is a need to take up systematic drought studies in India in order to evolve a suitable water distribution policy for different water uses linked with deficiencies in water supplies both surface and ground water for drought prone areas. Also there is a need to quantify the drought parameters keeping in view the future demand of the region. This will help in planning and design of water resources projects.