Journal of Irrigation and Drainage Engineering

Grain security is the foundation for national stability and prosperity. In China, grain production depends heavily on irrigation water, direct energy for machinery use, and indirect energy (such as fertilizers, pesticides, and agricultural film), resulting in growing pressure on water supply and demand and high carbon emissions. Therefore, it is urgent to study the regulation of planting structures to reduce the irrigation water input and carbon emissions on the premise of grain security. It is within the scope of the water–energy–food nexus. In China, water resources are mostly managed at the basin scale. Because of missing or inadequate basin-scale data, in this study, the Yellow River Basin (YRB) was chosen as an example to shed light on basin scale regulation analysis; YRB is an important grain production base in China, but it is facing serious water shortage and severe environmental problems. First, production and consumption of diverse grain species in the basin were estimated using remote sensing and statistical data simultaneously. Then, the blue water and carbon footprints were calculated to analyze the water use and carbon emission characteristics of grain production. Finally, the grain planting structure was regulated to reduce the irrigation water input and carbon emissions. Our findings suggest that, with effective planting structure regulation, $4.11\times {10}^8{\mathrm{m}}^3$ irrigation water and $16.98\times {10}^4\mathrm{tons}$ ${\mathrm{CO}}_2$ equivalents could be reduced and the grain production increased by about $31\times {10}^4\mathrm{tons}$ in the YRB. This study can be viewed as a step towards the use of multisource data to facilitate the analysis of diverse grain species characteristics and sustainable grain development while considering the water–energy–food nexus. A combination of effective planting structure regulation in arid regions and policies will contribute to an increase in grain production as well as saving of resources.

The effect of permeable pavement in reducing stormwater runoff is dependent on its infiltration performance. The monitoring and modeling methods were adopted to analyze infiltration performance of permeable pavement and was primarily based on Darcy’s law in previous studies. But Darcy’s law disregards the changing infiltration rate with the change of water content in permeable pavement medias. Neglecting the infiltration rate change frequently resulted in significant deviation between the monitoring and modeling results. To address these issues, the accuracy of two modeling methods for the infiltration performance of permeable brick pavement system ($PBPs$) was evaluated. The first is the low impact development ($LID$) module of the stormwater management model ($SWMM$), and the second is a new equivalent modeling approach based on the Horton model for $PBPs$. According to the results, the Horton model accurately described the infiltration performance of $PBPs$ in $SWMM$. Under high return periods situation, the coefficients of determination ($R^2$) and Nash-Sutcliffe efficiency coefficients ($E_{ns}$) reach 0.82 and 0.88, respectively, and the simulation error ranges from 6.57% to 8.75%. The experimental and simulation results of the $LID$ module in $SWMM$ were compared in greater detail. The result demonstrated that the $LID$ module of $SWMM$ underestimated the infiltration capacity of $PBPs$ because it ignored the fluctuating infiltration rate throughout the whole $PBPs$ infiltration process. Therefore, the proposed equivalent modeling method is superior to simulating the infiltration performance of $PBPs$ in $SWMM$, and the Horton model improved the simulation accuracy of $PBPs$ infiltration.

Abstract

The development of wetting zone in soil under drip irrigation is an important design parameter that is difficult to determine a priori. Using Hydrus-two-dimensional (2D), this paper studied water movement emanating from the drip emitter under different conditions, from which we proposed an improved dimensional model to calculate the radius and depth of the wetting zone using initial soil water content, saturated hydraulic conductivity, irrigation amount, and dripping rate as independent variables. The accuracy of the model was validated against experimental data published in the literature and measured by us. The results show that, compared with experimental data, the root mean square error of the wetting radius and depth estimated using the proposed model are 3.05 cm and 4.76 cm, respectively, with their associated Nash efficiency coefficient being 0.805 and 0.767, respectively. Compared with existing dimensional models that do not consider initial soil moisture prior to irrigation, the proposed model is more accurate and can be reliably used for drip irrigation design.

Practical Applications

The development of wetting zone and its final shape on the soil surface under drip irrigation is an important parameter to design the distance between emitters but difficult to determine analytically because of the complexity and nonlinearity of soil water flow. Based on previous work, this paper proposes an improved dimensional model to analytically calculate the size of the wetting zone. The model is mathematically simple and uses initial soil moisture content, saturated hydraulic conductivity and irrigation amount as independent variables. The soil physical parameters (saturated hydraulic conductivity and soil matrix potential) in the proposed model can be easily obtained through conventional field experiments. Test against experimental data measured by us and published in the literature for different soils shows that the proposed model is more accurate and robust than existing models and can be used to help design drip irrigation in different soils.

A double rubber dam with the upper dam inflated by air and lower dam inflated by water is proposed in this paper. Large-scale physical hydraulic model tests are carried out to investigate the influence of the inflated air and water pressures, external water levels, anchoring distances, and cross-sectional perimeter ratios on the static response of the proposed structure. This study reveals that the optimum inflated air pressure in the upper dam is $0.25{\gamma }_{\mathrm{w}}{L}_1$ and that in the lower dam is $0.45{\gamma }_{\mathrm{w}}{L}_1$, where ${\gamma }_{\mathrm{w}}$ and $L_1$ are the unit weight of water and perimeter of the upper dam. The optimum anchoring distance is $0.06L_1$, and the optimum perimeter ratio of the lower to upper dams is 0.9. Under the same external water depth, the material requirements of the proposed rubber dam are 105.8%–126% of the traditional rubber dam, and the tensile strength is 29.6%–48.8%. Considering the perimeter and tensile strength requirements, the total material costs of the air- and water-inflated double rubber dams are only 11.5%–24.2% of the traditional rubber dam.