NSE (Control grade,>96%)

In any agricultural watershed, best management practices (BMPs) are a conservational way to reduce non-point source pollution and, soil and water resources sustainability. The objectives of this study were to calibrate and validate the modified Soil and Water Assessment Tool (SWAT) in the Violada Watershed (VW), Spain and assess the BMPs scenarios, already tested at field scale, using the Decision Support System for Agro Technology Transfer model (DSSAT), and finally, to access the BMPs impact on water quality off-site. To this end, daily streamflow discharge and NO3- concentration were measured at VW outlet from October 2015 to September 2017 for model evaluation. The SWAT-CUP was used for sensitivity analysis, calibration and validation for both measured variables alter manual calibration of the main crops yield. Three management scenarios were compared to the current conditions (baseline): (i) recommended N fertilization, (ii) optimum irrigation and: (iii) combined recommended N fertilization and optimum irrigation (combined BMPs). The SWAT crop growth model calibration demonstrated that the annual average of crop yield and actual evapotranspiration estimations were satisfactory. Monthly calibration and validation results were satisfactory for streamflow discharge and NO3-N load, with Nash-Sutcliffe efficiency (NSE) according to the criteria reported in the literature. The two individual scenarios results showed difference in their environmental impact and therefore combined BMPs scenario was considered more efficient in reducing NO3-N load (51%) than the recommended N fertilization (36%) and the optimum irrigation (12%), while including all additional environment and farmers' benefits of both individual scenarios. Under this combined scenarios, all crops yields were maintained or increased, and the total irrigation water and N mineral fertilizers application reduction were about 5% and 27%, respectively. However, further work is still needed to consider additional BMPs to limit the soil N residual losses during the non-cropped period. The applied methodology can be a good alternative for improving water quality in similar irrigated watersheds. (C) 2020 Elsevier B.V. All rights reserved.

Effective soil thermal conductivity (lambda(eff)) is required by a variety of science and engineering studies and associated numerical simulations. Because water content is the dominant factor determining the magnitude of lambda(eff), modeling of lambda(eff) is usually based on the measured water content (theta) or degree of saturation (S-r). However, these approaches are largely soil dependent and no model was found for universal application. Prediction of lambda(eff) from energy states of soil water (i.e., psi, the matric potential or matric suction) provides a unique way that takes pore size and geometry of soil into account and the resultant lambda(eff)(psi) relationship is less sensitive to soil types compared to the lambda(eff)(theta) and lambda(eff) (S-r) relationships. The lambda(eff)(psi) relationship developed by McCumber and Pielke (1981) (MP1981) has been incorporated into over 10 land surface, climate or hydrological models for wide applications. But the MP1981 model was reported to give unreasonable estimates especially at low psi range. Lu a al. 2019 (LS2019) proposed an improved lambda(eff)(psi) model but limited to applications in high psi range. The objective of this study was to develop a new lambda(eff)(psi) model for applications across the full range of matric potential. Experimental measurements of lambda(eff)(psi) taken on 26 soils from four studies were used for the model development. A comparison of the new model with the MP1981, LS2019 and three other literature models showed the new model gave satisfactory estimates (RMSE < 0.2 W m(-1) degrees C-1, AD approximate to 0 W m(-1) degrees C-1 and NSE > 0.9) that outperformed all the other models. However, there is a lack of experimental measurements of lambda(eff)(psi) to further validate and calibrate this model. Future efforts on the measurement of lambda(eff)(psi) should be conducted and studies that investigate the effects of air entry and hysteresis on the behavior of lambda(eff)(psi) relationship is recommended.