applied sciences  
Article  
Predicting Climate Change Impact on Water Productivity of  
Irrigated Rice in Malaysia Using FAO-AquaCrop Model  
[PERSON] 1,2, [PERSON] 1,*, [PERSON] 3, [PERSON] 1 and [PERSON] 4  
Department of Biological and Agricultural Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang 43400, Malaysia; [EMAIL_ADDRESS] (A.A.H. ); [EMAIL_ADDRESS] (M.A.M.Z.) Department of Soil and Water, Faculty of Agriculture, Sebha University, Sebha, Lihya 3 Department of Irrigation and Water Management, Bangladesh Agricultural University, Mymensingh 2022, Bangladesh; [PERSON]AIL_ADDRESS] Department of Civil Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang 43400, Malaysia; [EMAIL_ADDRESS] Correspondence: [EMAIL_ADDRESS]; Tel. : +60-3-9769-6424  
Water productivity (WP) is a key indicator of agricultural water management, since it affects the quantity of water used for crop yield in various management scenarios. This study evaluated the WP of irrigated rice due to a changing climate in the Northwest Selangor Rice Irrigation Scheme (NSRIS) by using field experimental data and the FAO-AquaCrop Model. Pertinent soil, water, climate, and crop data were acquired by executing a field investigation during the off-season (dry season, January-April) and main season (wet season, July-October) in 2017. The AquaCrop 6.0 model was calibrated and validated using the measured data. A Climate-smart Decision Support System (CSDSS) with an ensemble of 10 Global Climate Models (GCMs) was used to downscale climate variables under RCP4.5, RCP6.0, and RCP8.5 emission scenarios during baseline (1976 to 2005) and future (2020 to 2099) periods. The AquaCrop model fairly predicted rice yields under field conditions with root-mean-square error (RMSE), mean absolute error (MAE), prediction error (PE) and index of agreement (d) between the observed and estimated yields of 0.173, 0.157, \(-\)0.31 to 5.4 and 0.78, respectively for the off-season; and 0.167, 0.127, \(-\)5.6 to 2.3 and 0.73, respectively for the main season. It predicted a 10% decrease in actual crop evapotranspiration (\(ET_{c}\)) in both crop seasons in the future. The WP of rice based on total water input (\(WP_{IP+RF}\)), applied irrigation (\(WP_{IP}\)), and actual crop evapotranspiration (\(WP_{ET}\)) will likely increase by 14-24%, 14-19%, and 17-29%, respectively under the three RCP emission scenarios in the off-season. The likely increase in WP for the corresponding base is 13-22%, 15-24%, and 14-25% in the main season. Various agronomic management options linked to WP will most likely become important in making crucial decisions to cope with the risk of impacts on climate change. water productivity; rice irrigation; climatic impact; AquaCrop model; CSDSS; Malaysia 40.0000-0001-990-0001-990-0001-990-0001-99001-99001-99001-99001-99001-9901-99001-99001-99001-9901-9  
between 17.1% and 36.3% among the watersheds, and between 22.9% and 45.4% among the coastal regions. There will be a 2.52 \({}^{\circ}\)C to 2.95 \({}^{\circ}\)C increase in the ensemble average of the basin-average annual mean air temperature between the years 2010 and 2100 [5]. Malaysia has an equatorial climate; it is therefore hot and humid for most of the year. The daily temperature ranges from 21 \({}^{\circ}\)C to 32 \({}^{\circ}\)C throughout the year. Peninsula Malaysia receives an average of 2500 mm rain annually. On average, Malaysia's current total rice import is 700,000 to 900,000 MT per year [6]. Water productivity (WP) is an important indicator of water usage [7], and hence, its improvement is crucial for sustainable agricultural water management and food security [8]. WP varies with crops and climatic conditions, irrigation systems, water management, and agricultural practices, among different fields [9,10]. The potential impact of climate change is expected to modify both water demand and supply patterns for agriculture.