Groundwater use for irrigation - a global inventory

Irrigation is the most important water use sector accounting for about 70% of the global freshwater withdrawals and 90% of consumptive water uses. While the extent of irrigation and related water uses are reported in statistical databases or estimated by model simulations, information on the source of irrigation water is scarce and very scattered. Here we present a new global inventory on the extent of areas irrigated with groundwater, surface water or non-conventional sources, and we determine the related consumptive water uses. The inventory provides data for 15 038 national and sub-national administrative units. Irrigated area was provided by census-based statistics from international and national organizations. A global model was then applied to simulate consumptive water uses for irrigation by water source. Globally, area equipped for irrigation is currently about 301 million ha of which 38% are equipped for irrigation with groundwater. Total consumptive groundwater use for irrigation is estimated as 545 km3 yr−1, or 43% of the total consumptive irrigation water use of 1 277 km3 yr−1. The countries with the largest extent of areas equipped for irrigation with groundwater, in absolute terms, are India (39 million ha), China (19 million ha) and the United States of America (17 million ha). Groundwater use in irrigation is increasing both in absolute terms and in percentage of total irrigation, leading in places to concentrations of users exploiting groundwater storage at rates above groundwater recharge. Despite the uncertainties associated with statistical data available to track patterns and growth of groundwater use for irrigation, the inventory presented here is a major step towards a more informed assessment of agricultural water use and its consequences for the global water cycle

The use and re-use of unsustainable groundwater for irrigation: A global budget

Depletion of groundwater aquifers across the globe has become a significant concern, as groundwater is an important and often unsustainable source of irrigation water. Simultaneously, the field of water resource management has seen a lively debate over the concepts and metrics used to assess the downstream re-use of agricultural runoff, with most studies focusing on surface water balances. Here, we bring these two lines of research together, recognizing that depletion of aquifers leads to large amounts of groundwater entering surface water storages and flows by way of agricultural runoff. While it is clear that groundwater users will be impacted by reductions in groundwater availability, there is a major gap in our understanding of potential impacts downstream of groundwater pumping locations. We find that the volume of unsustainable groundwater that is re-used for irrigation following runoff from agricultural systems is nearly as large as the volume initially extracted from reservoirs for irrigation. Basins in which the volume of irrigation water re-used is equal to or greater than the volume of water initially used (which is possible due to multiple re-use of the same water) contain 33 million hectares of irrigated land and are home to 1.3 billion people. Some studies have called for increasing irrigation efficiency as a solution to water shortages. We find that with 100% irrigation efficiency, global demand for unsustainable groundwater is reduced by 52%, but not eliminated. In many basins, increased irrigation efficiency leads to significantly decreased river low flows; increasing irrigation efficiency to 70% globally decreases total surface water supplies by backsim600 km3 yr−1. These findings illustrate that estimates of aquifer depletion alone underestimate the importance of unsustainable groundwater to sustaining surface water systems and irrigated agriculture

The socio-ecology of groundwater in India

Groundwater irrigation / Groundwater development / India

Assessment of groundwater extraction in the Tadla irrigated perimeter (Morocco) using the SSEBI remote sensing algorithm

In the Tadla irrigation perimeter, farmers supplement their irrigation supplies with groundwater, leading to water table depletion in the area. An additional concern is the deteriorating water quality in the area. There is no regulation to control withdrawals of groundwater, and no data are available to quantify groundwater use. The paper demonstrates a method based on remote sensing techniques and field observation data to estimate the ground water use for the 2006 hydrological year. Calculations show that for Tadla, average groundwater use amounts to around 55% of the surface irrigation water use. This is substantial, and requires immediate attention. Policy recommendations are needed to control the use of groundwater and to reach an integral management with the canal water. For exact calculations, data on groundwater levels are needed

Performance evaluation of the Bhakra Irrigation System, India, using remote sensing and GIS techniques

Irrigation systems / Irrigation canals / Irrigation scheduling / Performance evaluation / Remote sensing / GIS / Irrigated farming / Satellite surveys / Sustainable agriculture / Productivity / Groundwater / Salinity / Crop yield / Wheat / Surface irrigation / India / Bhakra Irrigation System

Improving performance and financial viability of irrigation systems in India and China

Irrigation systems / Groundwater irrigation / Energy / Cost recovery / India / China

A Study on Evolving Optimal Cropping Patterns in Groundwater Over-exploited Region of Perambalur District of Tamil Nadu

Falling groundwater tables and depletion of economically accessible groundwater resources would have major social and economic consequences. The present study has been taken up with the overall objective of evolving optimal crop plans to sustain the use of groundwater resources for irrigation. Perambalur district was purposively selected for the study as it mainly depends on groundwater for its irrigation. Linear programming technique was used to evolve optimal crop plans. The constraints identified were primarily irrigation water, besides land availability during the cultivating seasons and capital. Six typical farms were selected, one each for the open well, wells in tank command area and tubewell-irrigated farms in critical and over-exploited groundwater regime and also for semi-critical and safe groundwater regime. The results of the optimal crop plans derived showed that the irrigation water-use in the critical period could be reduced by 24.30, 4.54 and 51.71 hours of pumping in ordinary wells, wells in tank command area and tubewell-irrigated farms, respectively in critical and over-exploited groundwater regime sample farms. In the semi-critical and safe groundwater regime sample farms, the optimal crop plans revealed that the irrigation water-use in the critical period could be reduced by 4.61, 3.99, and 4.73 hours of pumping in ordinary wells, wells in tank command area and tubewell-irrigated farms, respectively. Area under high water intensive crops namely, paddy and sugarcane declined almost in all the optimal crop plans. Area under low water intensive crops (groundnut, gingelly and tapioca) showed an increasing trend in all optimal crop plans. The net income of the sample farms increased marginally or considerably in the optimal crop plans of both the critical and overexploited groundwater regime sample farms and semi-critical and the safe groundwater regime sample farmsAgricultural and Food Policy,

PROJECTED USE OF GROUNDWATER FOR IRRIGATION IN THE TEXAS HIGH PLAINS

Projections of groundwater irrigation under alternative price conditions are computed for representative resource situations in the Texas High Plains. The rate of groundwater depletion and pumping costs are related to the level of irrigation pumpage over the period 1976-2026. The projected economic life of irrigation in this region is responsive to changing economic conditions; in particular, the rate of increase in energy prices for pumping.Resource /Energy Economics and Policy,

Regional assessment of groundwater recharge in the lower Mekong Basin

Groundwater recharge remains almost totally unknown across the Mekong River Basin, hindering the evaluation of groundwater potential for irrigation. A regional regression model was developed to map groundwater recharge across the Lower Mekong Basin where agricultural water demand is increasing, especially during the dry season. The model was calibrated with baseflow computed with the local-minimum flow separation method applied to streamflow recorded in 65 unregulated sub-catchments since 1951. Our results, in agreement with previous local studies, indicate that spatial variations in groundwater recharge are predominantly controlled by the climate (rainfall and evapotranspiration) while aquifer characteristics seem to play a secondary role at this regional scale. While this analysis suggests large scope for expanding agricultural groundwater use, the map derived from this study provides a simple way to assess the limits of groundwater-fed irrigation development. Further data measurements to capture local variations in hydrogeology will be required to refine the evaluation of recharge rates to support practical implementations