Conceptualizing the climate change perspective of crop growth and evapotranspiration (ETc) rates and subsequent irrigation water requirements (IWR) is necessary for sustaining the agriculture sector and tackling food security issues in Pakistan. This article projects the future growth periods and water demands for the wheat-rice system of Punjab. Intense and hotter transitions in the future thermal regimes and erratic monsoon rainfall increments were envisaged. The crop growth rates were accelerated by the probable temperature rise resulting in shortened growth periods. The temperature rise increased the reference evapotranspiration rates; however, the future ETc declined due to reduced growth period and net radiation. Highly unpredictable, but mostly increasing, cumulative seasonal and annual rainfalls were indicative of more effective rainfalls during the future crop seasons. Reduced ETc and increments in seasonal effective rainfalls gave rise to the declining IWR for both crops. The study findings seemingly undermined the harmful climate change influences on the water requirements of the wheat-rice system of Punjab but alarmingly shortening of growth periods indicates a higher crop failure tendency under the projected future thermal regime.

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This article analyzed the wheat yield variabilities and water footprints under projected future climate based on wheat yield sensitivity to past (1980–2017) trends of maximum temperature (Tmax), minimum temperature (Tmin), solar radiation (Rn) and rainfall (P) for the semi-arid condition of Punjab, Pakistan. The past and projected future trends of the climate variables were identical featuring prominent Tmin rise than Tmax accompanied by Rn and P declines. Based on the past influences and the projected future trends of the climate variables, Tmin was the principal driver of wheat yield decline followed by the Tmax, P and Rn. Wheat evapotranspiration and net irrigation water requirement declined due to the influence of both decrease of growing season length and Rn for the first half of 21st-century, and this trend reversed during the second half of 21st-century. These phenomena were caused by different degree of climate warming between the two-time slices. Due to future wheat yield decline and a gradual rise in green water scarcity the blue and grey water footprints rise consistently particularly during 2nd-time slices. CO2 enrichment showed limited mitigation potential of nullifying the warming-induced threats on future wheat yield and water footprints.

Technological development and climate change dictate farming practices, which can directly affect irrigation water requirement and supply. In this article, the water supply reliability (WSR) of 62 major Korean agricultural reservoirs was comprehensively evaluated for varying climate and farming practices. Field surveys identified the recent divergence from standard rice farming practices and a 45-year daily weather data set (1973–2017) was examined to understand the phenomenon of climate change. Effective rainfall increments mitigated the imminent surges in rice irrigation water requirements driven by warming-led accelerated crop evapotranspiration rates; therefore, climate change marginally influenced the WSR of selected reservoirs. The transplanting period and associated water consumption were the primary deviations from standard rice farming practices. A significantly prolonged transplanting period seriously compromised the WSR of agricultural reservoirs and the maximum number of unsafe reservoirs was detected for a 24-day increase in the transplanting period. A watershed/irrigated area ratio of less than 2.5 was the lower threshold below which all the reservoirs had unsafe WSR regardless of the climate change and/or farming practices. Recent variations in farming practices were the primary cause of reservoir failure in maintaining the WSR.