Assessment of dry and wet periods using selected rainfall-based drought indicators – a case study

Abstract

ABSTRACT Knowledge on dry and wet periods of a region or station is essential for effective formulation of policies for water use, agriculture and economics. Dry and wet periods are the recurrent features for the majority of India and those areas depend on monsoon rainfall to fulfil domestic, industrial, and agricultural water requirements. Rainfall varies both in space and time and causes dry and wet periods. These dry and wet periods are generally assessed using drought indicators. The objectives of the present research are (a) to evaluate such periods for Thanjavur city using Standardized Precipitation Index (SPI), Statistical Z-score index and China Z-index, and (b) to make comparisons of these indicators in different time-scales. The results of the study indicate that China Z-index and Statistical Z-score are close to each other for annual and seasonal rainfall data and they are different from SPI. Monthly moisture categorizations based on these three indicators are distinct from each other. Further, the study confirms that China-Z-index is more appropriate to address the moisture category for those periods in which the rainfall is highly erratic.