The Impacts of Climate Variability on Crop Yields and Irrigation Water Demand in South Asia

Abstract

Accurate (spatio-temporal) estimation of the crop yield relation to climate variables is essential in the densely populated Indus, Ganges, and Brahmaputra (IGB) river basins of South Asia for devising appropriate adaptation strategies to ensure regional food and water security. This study examines wheat (Triticum aestivum) and rice (Oryza sativa) crop yields’ sensitivity to primary climate variables (i.e., temperature and precipitation) and related changes in irrigation water demand at different spatial (i.e., province/state, districts and grid cell) and temporal (i.e., seasonal and crop growth phase) scales. To estimate the climate driven variations in crop yields, observed and modelled data applying the Lund-Potsdam-Jena managed Land (LPJmL) model are used for six selected study sites in the IGB river basins over the period 1981–2010. Our statistical analysis underscores the importance of impacts assessments at higher spatio-temporal scales. Our grid cell (aggregated over study sites) scale analysis shows that 27–72% variations in wheat and 17–55% in rice crop yields are linked with temperature variations at a significance level of p < 0.001. In the absence of irrigation application, up to 39% variations in wheat and up to 75% variations in rice crop yields are associated with precipitation changes in all study sites. Whereas, observed crop yields show weak correlations with temperature at a coarser resolution, i.e., up to 4% at province and up to 31% at district scales. Crop yields also showed stronger sensitivity to climate variables at higher temporal scale (i.e., vegetative and reproductive phases) having statistically strong negative relationship with temperature and positive with precipitation during the reproductive phase. Similarly, crop phase-specific variations in climate variables have considerable impacts (i.e., quantity and timing) on irrigation water demand. For improved crop water planning, we suggest integrated climate impact assessments at higher spatio-temporal scales which can help to devise appropriate adaptation strategies for sustaining future food demand.

Influence of long-term intensive use of irrigated meadow-chernozem soil on the biological activity and productivity of the arable layer

“…The climatic conditions, especially the rainfall in the vegetation period have a significant impact on the plant development and their yeild 12 . The lack of moisture reduces the availability of mineral nutrition elements, including phosphorus, and changes the potential mechanisms of its replenishment in the soil solution 13 .…”

Regional and Seasonal Precipitation and Drought Trends in Ganga–Brahmaputra Basin

“…Rice and wheat are major crops cultivated in the Ganga-Brahmaputra Basin. Change in precipitation patterns and climate variability affect crop yields, and impact is more intense in regions with no irrigation facilities [33]. The development of appropriate adaptation measures is necessary to mitigate the impacts of climate variation in crop yield.…”

“…Location, along with average annual precipitation and elevation of GB basin, are shown in Figure 1. Precipitation deficiencies have affected crop yields [33], hydroelectricity generation [34], groundwater storage [35], etc. in the Ganga-Brahmaputra Basin and its tributaries.…”

“…2006 and 2009 droughts had a significant detrimental impact on the groundwater storage in the Ganga-Brahmaputra Basin [35]. Precipitation deficiencies have affected crop yields [33], hydroelectricity generation [34], groundwater storage [35], etc. in the Ganga-Brahmaputra Basin and its tributaries.…”

“…Although most of the southern basin has the potential to be irrigated, a large portion of the basin does not have irrigation facilities [34]; moreover, droughts and changes in precipitation patterns make agriculture in unirrigated areas more vulnerable. According to Ahmad et al [33], precipitation fluctuations can cause up to 39 percent variations in wheat production and up to 75 percent variations in rice production in regions with no artificial irrigation facilities in the Ganga-Brahmaputra Basin [33].…”