Impact of climate change on agricultural water demand in selected areas of Bangladesh

Abstract

In recent times, several studies around the globe show that climatic change is likely to impact significantly upon freshwater resources availability. Demand for water has already increased manifold over the years due to urbanization, agriculture expansion, increasing population, rapid industrialization and economic development. At present, changes in cropping pattern and land-use pattern, over-exploitation of water storage and changes in irrigation and drainage are modifying the hydrological cycle in many climate regions and river basins. This research examines changes of water requirement due to climate change. Outputs of HadCM2 and UKTR model were used to evaluate the impact of climate change on evapotranspiration. The climatic parameters of temperature, precipitation, relative humidity, sunshine duration and wind speed, climate scenarios from model were incorporated into the CROPW AT model and used to evaluate the potential impact of climate change on evapotranspiration to simulate the total CWR for the present and the future years in study area. This model calculated crop water requirements ofrnajor crops B.Aus, T.Aman and Boro. From output value of HadCM2 the result shows that an increase in evapotranspiration increases the percentage change in crop water requirements in 2050 and 2070. Under current climate conditions, the average reference evapotranspiration (ETo) is 3.26 mm /day which will rise to 3.39mm/day in 2050 and 3.5 mm/day in 2070 which indicates average ETo will be 4.17 % more in 2050 and 7.49% higher in 2070 than that of the base climate condition at present. In addition, CWR of major season growing crops will also increase around 4% and 8% in 2050 & 2070 respectively. Results found from UKTR model are quite same. But increment of CWR found from HadCM2 in 2070 is more than that found from UKTR model. Crop water demand must be met as this strongly determines crop emergence, development and survival in the tropical regions. However, more accurate knowledge about crop response to water is essential in a range of crops for applications for policies and investment strategies at national level. The information obtained from this research enhances understanding of crop water requirements, which will consequently help improve the productivity of both food and cash crops.