Scientific evaluation of crop water use efficiency is of great significance for ascertaining water-saving potential and realizing efficient utilization of water resources. In this paper, we calculated the water footprint of crop growth, pollution water footprint and production water footprint of 14 cities in Liaoning Province, China, by using the water footprint theory, established the crop water use efficiency model of stochastic frontier distance function, and analyzed the spatial-temporal variation characteristics of crop water use efficiency (WUE), ecological WUE and production WUE. Results show that: (1) the average water footprint of crop growth was 1.714 × 10⁹ m³, the ecological water footprint of crop was 6.26 × 10⁸ m³, and the water footprint of crop production was 2.34 × 10⁹ m³ from 2001 to 2017 for the whole province. (2) the WUE of crop growth was 0.821, the crop ecological WUE was 0.845 and crop production was 0.865, respectively. We concluded that Liaoning province can save 17.9% of crop consumption water, equivalent to 8.38 × 10⁸ m³, 15.5% of ecological water, equivalent to 7.25 × 10⁸ m³ and 13.5% of production water, equivalent to 6.32 × 10⁸ m³ by strengthening the popularization of agricultural high-efficiency water use technology and improving the level of policy management. This research provides a basic support for the evaluation of crop water-saving potential with the stochastic frontier approach in other regions.

The fundamental solution to the problem of emitter clogging is to explore the optimal structure design of emitter and improve its anti-clogging ability. The research objective was to select the optimal structural form of the emitter flow path in drip irrigation systems using inferior water sources, which can provide theoretical support for improving the anti-clogging ability of the emitter itself and designing new emitter products. The selection of the flow path structure of the emitter has not been conducted on the basis of determining the appropriate simulation model with the condition of complex water quality. Therefore, the appropriate internal fluid movement model of the emitter was determined, the hydraulic performance and anti-clogging performance of the five nationally and internationally representative flow path structures were comprehensively evaluated, and finally the optimal structure of the emitter flow path was determined. The research results indicated that RNG k - ε model was the most suitable to simulate the flow field in the emitter by comprehensive analysis of the gap between simulated values and the measured values, the calculation accuracy and computational efficiency. The fractal flow path was relatively optimal for hydraulic performance and for anti-clogging performance. This study can provide theoretical support for improving the anti-clogging ability of the emitter itself and the design of the new emitter product.

(1) Setting a matrix dam in the paddy field drainage ditch has been recognized as an effective method to lower the velocity of water discharged from a paddy field in the drainage ditch, which can improve the purification efficiency of the drainage ditch for nitrogen and phosphorus pollutants, but the specific placement and thickness of the matrix dam have not been supported due to the insufficient research results. (2) Three thicknesses of the matrix dam were set in three locations of the physical model of the drainage ditch. By measuring the flow rate and water level in different sections, the optimal layout location and thickness of the matrix dam were determined. (3) When the matrix dam was located in section 1-1, the flow rate from sections A-A to C1-C1 was reduced by 0.159 m/s; when the matrix dam was located in section 2-2, the flow rate was reduced by 0.331 m/s; when the matrix dam was located in section 3-3, the flow rate was reduced by 0.360 m/s. (4) We concluded that the optimal design position of the matrix dam was section 3-3, 9.2 m from the entrance of the water flume, and the optimal design thickness was 0.3 m.