A methodology to estimate equity of canal water and groundwater use at different spatial and temporal scales: a geo-informatics approach

Abstract

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