Assessing potential water savings in agriculture on the Hai Basin plain, China

• An approach to evaluate the potential amount of water saving at the basin scale.
• The potential water savings for the optimum options of interventions.
• Reducing the water deficit in the Hai Basin will require a significant reduction.

The Hai Basin in China exemplifies problems that are observed in many arid environments: excessive water consumption, depletion of aquifers, and damage to eco-systems. Progressively since the 1970s water resources in Hai Basin have been over-exploited, primarily for irrigation, while the water requirements of other sectors have increased. Water tables are falling and outflows to the sea are sporadic and heavily polluted. Current consumption of water in the basin is estimated to exceed the renewable supply from rainfall by 6.25 × 109 m3 yr−1. Traditional approaches—improving irrigation efficiency through structural works and on-farm technologies such as drip and sprinkler—have failed to restore a balance. Researchers have investigated various on-farm techniques to reduce consumption, including mulching, zero tillage, deficit irrigation, revised cropping patterns, and improved cultivars. We project the results of such experiments for winter wheat (Triticum aestivum L.), maize (Zea mays L.), and cotton (Gossypium spp.) to basin scale to assess their potential in restoring sustainable water consumption. Widespread adoption of mulching, which is the most promising option for farmers, would reduce the over-consumption by 25% (1.6 × 109 m3 yr−1). If water quotas are introduced, forcing a reduction in consumption, current production could be maintained while saving 4.1 × 109 m3 yr−1. Ending the remaining over-consumption of 2.15 × 109 m3 yr−1 would require reducing grain production by 4–7.8 Mt yr−1.