Scale Effects of Water Saving on Irrigation Efficiency: Case Study of a Rice-Based Groundwater Irrigation System on the Sanjiang Plain, Northeast China

Abstract

This research analyzed the scale effect of water saving in Bielahonghe (BLH) Basin, a rice-cultivating district on the Sanjiang Plain, Northeast China. Water budgets with different surface irrigation water supply ratios and water-saving measures were simulated with a semi-distributed water balance model. PF nws , representing the ratio of rice evapotranspiration to net water supply (the total amount of irrigation and precipitation minus the amount of water reused), was employed to assess the water use efficiency. Seven spatial scales (noted from S1 to S7), ranging from a single field (317.87 ha) to the whole basin (about 100,800 ha) were determined. PF nws values were quantified across scales and several water-saving measures, including water-saving irrigation regimes, canal lining, and a reduction of the surface water supply ratio (SWSR). The results indicated that PF nws increased with scale and could be calculated by a fitted power function (PF nws = 0.736Area 0.033 , R 2 = 0.58). Furthermore, PF nws increased most prominently when the scale increased from S1 to S2. The water-saving irrigation regime (WSIR) had the most substantial water-saving effect (WSE) at S1. Specifically, PF nws improved by 21.2% at S1 when high-intensity WSIR was applied. Additionally, the WSE values of S3 and S5 were slightly higher than at other scales when the branch canal water delivery coefficient increased from 0.65 to 0.80 through canal lining. Furthermore, the PF nws at each scale varied with SWSR. Specifically, PF nws from S3 to S7 improved as SWSR decreased from 0.4 to 0.3 but remained approximately constant when SWSR decreased from 0.3 to 0.

A Comprehensive Modelling Approach to Assess Water Use Efficiencies of Different Irrigation Management Options in Rice Irrigation Districts of Northern Italy

“…To solve the issue, the following approach was implemented, by recurring to an ad hoc set of 4th order polynomial curves (SP4 hereafter). For each month (supposed to be 30 days long), the five parameters of the SP4 were obtained by solving a linear equations system containing the following conditions: (14) where y n (x) is the value of the SP4 of the n-th month at the t-th day of the month (going from 0 to 29), m n is the monthly mean given by the PGL model for the n-th month. At the end of December, a null derivative was imposed.…”

“…Values of WUE found for the whole study area (512 ha) are about 30% and 50% for traditional flooding and aerobic rice, respectively. In a more recent study conducted in northeast China [14], the authors estimated the WUE at seven different spatial scales, ranging from about 300 ha (the total area served by a single branch ditch) to 100,800 ha (the whole irrigation basin) by applying a distributed water balance model which takes into account a share of reused water from ditches and groundwater contribution. The results showed an increase of WUE values from 66% at the field scale to 90% at wider scales.…”

Methodologies for the Sustainability Assessment of Agricultural Production Systems, with a Focus on Rice: A Review

“…While some of the farm-level indicators can be used to describe an agricultural system also at larger spatial scales (e.g., labor productivity, nutrient use efficiency), others may need to be revised as additional mechanisms and processes come into play at larger scales. For instance, in the case of environmental indicators dealing with water use in agricultural areas, it must be taken into account that percolation under the rooting zone and surface drainage can be seen as pure losses at the field scale, degrading efficiency, while at larger scales these same processes can be considered to contribute to groundwater recharge and to increase water availability for downstream areas, therefore increasing the efficiency of the system [67,68].…”

Cooling Effect of Paddy on Land Surface Temperature in Cold China Based on MODIS Data: A Case Study in Northern Sanjiang Plain

“…In terms of crop patterns, paddy, corn, and soybean were the main crops. Rice cultivation in the north of the Sanjiang Plain conforms to rice cultivation rules in cold regions [33][34][35], and rice is transplanted in mid May, usually between 15 May and 25 May. The harvesting date of rice was usually after 25 September and before 16 October (Figure 1).…”