摘要
Bangladesh has a large and growing population that will demand more food and place greater pressure on resources. Dry season irrigated Boro rice production is important for national food security. Dry season irrigation mainly uses groundwater, but the extent of its use is not well known. We assessed groundwater use and water productivity of Boro in the northwest region of Bangladesh using remote sensing based energy balance modelling, crop classification and secondary statistics. The energy balance modelling shows a large spatial variation in the actual evapotranspiration (ETa) from about 325 to 470?mm, with an overall spatial average of 365?mm during dry season. The estimated values of ETa correspond well with independent values from field and regional scale soil and water balance modelling results. From spatial estimates of ETa and effective rainfall, we computed regional net groundwater use for Boro production in 2009 as 2.4?km3. Groundwater is being used unsustainably in some areas, and a spatial time series (1990 to 2010) of pre- and post-monsoon groundwater depth changes in the northwest region of Bangladesh suggests that, with the current level of groundwater use, falling groundwater levels may pose a long term threat to the sustainability of irrigated agriculture in much of the region. Boro water productivity varies from 0.95 to 1.35?kg/m3, allowing the identification of high performing “bright-and low performing “hot-spots and the development of strategies to reduce crop yield/productivity gaps and ensure future food security.