Modelling the Crop Water and Irrigation Requirements Using CROPWAT Model: A Case Study in Arid and Semi-Arid Regions of Pakistan

Abstract

Water is a key factor for successful crop cultivation. Declining water 
resources and increasing food demands require greater efficiency in water use, particularly in arid 
and semi-arid regions. Regulated deficit irrigation can reduce water consumption while minimizing 
adverse effects on yield. Models play a crucial role in developing practical recommendations for 
optimizing crop production under water-scarce conditions. This study estimates crop water 
requirements (CWRs), net irrigation requirements (NIRs), and effective rainfall (Peff) for wheat 
crop for the historical period (1986-2005) and four consecutive future time series (2020-2039, 2040
2059, 2060-2079 and 2080-2099) in arid (Bahawalpur) and semi-arid regions (Faisalabad) of 
Pakistan, using CROPWAT model. Results indicate that during the wheat growing season, CWR 
and NIR continued to increase. By the end of the 21st century, the CWR in semi-arid and arid areas 
of representative concentrated pathways (RCPs 4.5 and 8.5) increased by 3.01-6.86% and 2.46
5.64%, respectively. By 2099, under RCPs 4.5 and 8.5, the NIR in semi-arid and arid areas will 
increase by 5.49-10% and 2.41-5.86%, respectively. In the semi-arid and arid areas, the average 
seasonal Peff will be reduced by 9.79% (RCP 4.5), 10.07% (RCP 8.5), 2.81% (RCP 4.5), and 3.16% 
(RCP 8.5) respectively. Therefore, semi-arid areas will be more affected than arid areas, and changes 
in climatic conditions will threaten the agricultural system by reducing Peff.