A methodology to estimate equity of canal water and groundwater use at different spatial and temporal scales: a geo-informatics approach
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Indus basin irrigation system (IBIS) is one of the largest contiguous irrigation systems of the world. The surface canal water supplies are far less than the crop water demands which lead farmers to use groundwater to cope surface water scarcity. Although many studies in the IBIS are conducted to analyze the equitable distribution of canal water, there is hardly any study which comprehensively analyze the equitable use of canal water and groundwater at different spatial and temporal scales. One of the main reasons is lack of reliable information on the volume of groundwater abstraction. The objective of the current study is to develop an approach for estimating the equity of canal water and groundwater use at different spatial (canal command, distributaries, head, middle and tail end reaches) and temporal (daily, monthly and seasonal) scales of Hakra canal command area of IBIS. Results show that canal water and groundwater use to meet actual evapotranspiration is 34 and 42 %, respectively, which makes groundwater as an integral part of the large canal irrigation schemes of IBIS. The canal water and groundwater use varies significantly during the cropping colander. The maximum groundwater use is during May (51 mm) whereas the maximum canal water use is during August (24 mm). Farmers located at the head end reaches of Hakra canal use 42 % groundwater of total groundwater use whereas farmers located at the middle and tail end reaches use only 35 and 23 %, respectively. The canal water use at the head, middle and tail end reaches is 40, 34 and 26 %, respectively. These results show that the farmers located at the head of Hakra canal command area use more canal water and groundwater as compared to those located at the middle and tail end reaches. This methodology can provide guidelines to water managers in the region for equitable use of both canal water and groundwater.