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[EN] Agricultural economics Water Programming Models (WPM) has found that irrigators in water scarce areas have a rather inelastic response to water prices, making water pricing cost-ineffective towards water saving. We hypothesize that the predicted water saving performance of pricing is significantly underestimated by issues of model structure, due to the exclusion of deficit irrigation from the set of decision variables available to agents in conventional WPM. To test our hypothesis, we develop a model that integrates a continuous crop-water production function into a positive multi-attribute WPM, which allows us to assess agents¿ adaptive responses to pricing through deficit irrigation. The model is illustrated with an application to the El Salobral-Los Llanos irrigated area in Spain. Our results show that incorporating deficit irrigation as an adaptation option makes the water demand curve significantly more elastic as compared to an alternative model setting where deficit irrigation is precluded. We conclude that ignoring deficit irrigation can lead to a significant underestimation of the cost-effectiveness of water pricing towards water saving., The research leading to these results has received funding from the Program for the Attraction of Scientific Talent through the Project SWAN (Sustainable Watersheds: Emerging Economic Instruments for Water and Food Security), from the Biodiversity Foundation of the Spanish Ministry for Ecological Transition through the Project ATACC (Adaptacion ¿ Transformativa al Cambio Clim¿ atico en el Regadío) and from Programa Operativo FEDER Andalucía 2014-2020 through the project SEKECO (Evaluacion de estrategias de adaptacion a la sequía bajo el actual escenario de cambio climatico) Ref 1263831-R. This work was additionally supported by the ADAPTAMED (Design and evaluation of adaptation strategies to climate and global change in Mediterranean basins with intensive use of water for irrigation) national research project funded by the Spanish Ministry of Science and Innovation (RTI2018-101483-B-I00) with European FEDER funds.

The replacement of flood-irrigation systems by drip-irrigation technology has been widely promoted with the aim of a more sustainable use of freshwater resources in irrigated agriculture. However, evidence for an irrigation efficiency paradox emphasizes the need to improve our understanding of the impacts of irrigation transformations on water resources. Here, we developed a distributed hydrological modeling approach to investigate the spatiotemporal effect of flood and drip irrigation on groundwater recharge. The approach recognizes differences in the water balance resulting from the localized application of water in surface drip-irrigated fields and the more extensive application of water in flood irrigation. The approach was applied to the semi-arid Mediterranean region of Valencia (Spain) and calibrated using a multi-objective framework. Multiple process scales were addressed within the framework by considering the annual evaporative index, monthly groundwater level dynamics, and daily soil moisture dynamics. Daily simulations from 1994 to 2015 suggested that, in our hydroclimatic conditions, (a) annual recharge is strongly related to annual rainfall, which had a four times higher impact on recharge than the type of irrigation practice, (b) flood-irrigated recharge tends to exceed drip-irrigated recharge by 10% at annual time scales, (c) however, recharge response to a particular precipitation event is smaller in flood irrigation than in drip irrigation, and (d) 8-18 rainfall events could generate more than half of the annual recharge in drip and flood irrigation, respectively. Our results highlight the importance of understanding the hydrological dynamics under different irrigation practices for supporting irrigation infrastructure policies., Water Resources Research, 57 (8), ISSN:0043-1397, ISSN:1944-7973

Perennial ryegrass (Lolium perenne) is the predominant forage crop in the equatorial highland zones of Colombia due to its high nutritional value and versatility to produce both milk and meat. This study aimed to determine the relationship between the relative depletion of usable soil water and the Ks values of canopy expansion and closure stomatal of perennial ryegrass, as well as to identify the threshold values of water stress. The experiment was carried out in pots under a controlled environment condition. These pots were arranged in a completely randomized manner. The experiment consisted of five treatments—including control treatment—of water deficits in the soil that progressively increased the depletion level as the crop cycle developed. This generated a wide range of conditions in the growth stages. For each treatment, four repetitions were performed Biomass production was significantly affected by water stress. The results show that the upper and lower thresholds of Ks were 0.28 and 1.3 of the depletion level (p) of the total available water (TAW) in the soil for the expansion of the canopy (CE), and 0.25 and 1.1 p of the TAW for stomatal closure (gs). Quadratic functions were fitted for both the CE (R2 = 0.72) and CS (R2 = 0.73); moreover, the Ks function of FAO-AquaCrop with positive shape factor (sf) was as follows: sf = 11, RMSE 0.22 for CE, and sf = 4.3, RMSE 0.19 for gs. Our results indicate that ryegrass is moderately sensitive to water stress. The differences found between the Ks function of FAO and the experimental data call for the need to use modeling with parameters adapted for each case.

Forests play a determinant role in the hydrologic cycle, with water being the most important ecosystem service they provide in semiarid regions. However, this contribution is usually neither quantified nor explicitly valued. The aim of this study is to develop a novel hydro-economic modelling framework for assessing and designing the optimal integrated forest and water management for forested catchments. The optimization model explicitly integrates changes in water yield in the stands (increase in groundwater recharge) induced by forest management, and the value of the additional water provided to the system. The model determines the optimal schedule of silvicultural interventions in the stands of the catchment in order to maximize the total net benefit in the system. Canopy cover and biomass evolution over time were simulated using growth and yield allometric equations specific for the species in Mediterranean conditions. Silvicultural operation costs according to stand density and canopy cover were modelled using local cost databases. Groundwater recharge was simulated using HYDRUS, calibrated and validated with data from the experimental plots. In order to illustrate the presented modelling framework a case study was carried out in a planted pine forest (Pinus halepensis Mill.) located in south-western Valencia province (Spain).The optimized scenario increased groundwater recharge. This novel modelling framework can be used in the design of a “payment for environmental services” scheme in which water beneficiaries could contribute to fund and promote efficient forest management operations. This article is protected by copyright. All rights reserved.

[EN] Water-oriented forest management is an urgent need in semiarid catchments. In the case of low-biomass forests and shrublands, the magnitude, efficiency and temporal duration of thinning effects on rainfall partitioning needs further attention. This work studies the effects of juvenile thinning and shrub clearing on stemflow (Stf), throughfall (Thr) and interception (It) in two low-biomass forests (CAL: post-fire Aleppo pine saplings with 74% of basal area, BA, removed; and HU: evergreen oak coppice with 41% of BA removed), as well as the relative contribution of the event meteorology. The effects are compared with a control plot during the first 3¿4¿years. Stf rate (%) decreased with density and, on a tree scale, it was enhanced by the treatment only in the bigger oaks. Event Thr increased from 55 to 81% and from 68 to 86% of gross rainfall (Pg) for CAL and HU respectively after thinning, resulting in about 15% less intercepted Pg. High evaporative conditions and an open (ventilated) forest structure led to high It rates in the controls when comparing with other studies, thus making the treatments more efficient in net precipitation (Pn) gain (Pg intercepted decreased 17% or 2.3% per unit of LAI or BA removed respectively). In general, depths (mm) were mostly explained (>75%) by the rainfall characteristics of the event (e.g. amount, duration, intensity), with a limited contribution from forest structure (e.g. cover, LAI) and event meteorology (e.g. temperature, wind speed, vapor pressure deficit). On the contrary, when expressed as rates (% of Pg), forest structure and event-meteorology gained importance (explaining 25¿65%), especially in the drier site (CAL). In this site, the low gain in Pn (~25¿mm per year on average) was offset with no temporal dampening during the span of this study, as observed in the wetter site (HU), where plant growth tended to mitigate the effect of the treatment by the end of the study. The results presented here make a contribution to a better understanding of the effects of water-oriented forest management in low-biomass semiarid forests., This study is a component of research projects: HYDROSIL (CGL2011-28776-C02-02), SILWAMED (CGL2014-58127-C3-2) and CEHYRFO-MED (CGL2017-86839-C3-2-R) funded by the Spanish Ministry of Science and Innovation and the FEDER fund of the EU. The authors are grateful to the Valencia Regional Government (CMAAUV, Generalitat Valenciana), Serra municipality, VAERSA and ACCIONA for their support in allowing the use of the experimental forest and for their assistance in carrying out the fieldwork.

A pressurized irrigation network may operate in two ways, namely, on demand and organized under operating sectors. In the first case, the user decides when to irrigate, and the pumping station has to meet the discharge and pressure head requirements of the group of users that is demanding water at any time. In the second case, the operating hydrants at a given moment are previously established, which permits identification of scenarios related to lesser energy consumption. In this work, a new model was developed that identifies such scenarios. The optimization process is carried out by means of simulated annealing (SA). The model was applied to an example and the result obtained was compared with the same network operating on demand and sectorized using the criterion of hydrant elevation with respect to the pumping station. The scenario adopted for SA saved 11.8% and 15.5% in energy consumption compared with the two other scenarios, and decreased the installed power requirement by 38.3% and 21.6%, respectively.

The present work aims at approaching the study of the performance and uncertainty associated with an irrigation scheduling method based on a soil-water balance. On a daily time step, a water-balance-based irrigation scheduling model has been developed. A Monte Carlo simulation of the irrigation scheduling model is developed using a series of actual daily weather data of evapotranspiration and precipitation and bootstrapping stochastic technique to resampling them. Performance evaluation measurements and their uncertainty are studied by means of several parameters: reliability, resiliency, vulnerability, total irrigation water allocation, total water loosed by deep percolation, and actual evapotranspiration/potential evapotranspiration rate along the growing season. The behaviors of 12 different types of soils (between coarse-textured soils and fine-textured soils) are compared using pedotransfer functions. Total available water (TAW) is the most important hydraulic property of the soil as far as irrigatio...

The present work aims at taking us closer to the study of the influence of the spatial configuration of the irrigated zone on the unit cost (€/ha) of a layout irrigation network design. The layout ...

Traditional irrigation zones in the east of Spain have been denoted by the high level of parcellation. The layout of the irrigation network design in highly parcelled territories presents an important degree of difficulty, the previous experience of the designer in this task being crucial in the final result. In this work, a new heuristic algorithm for layout of the irrigation network design is presented. We start from a classical graph theory algorithm (Dijkstra’s algorithm) used for solving the shortest path spanning tree problem. This algorithm is modified to assign weights to the arcs and plot limits are used as if they were the arcs of a graph. The algorithm is implemented on a geographical information system, thus creating an application that automatically generates the layout of the irrigation network design. The only necessary initial data are the origin of the network (supply point) and the hydrants (delivery points). The advantage of this heuristic is that the subjectivity introduced for the des...

Location-allocation algorithms allow for situating services in an efficient way in zones where the demand is dispersed across the area. In the present work, the minisum location-allocation algorithm is used to optimize the placement multioutlet hydrants, which are needed to supply irrigation to the region. The objective function aims to minimize the total access costs of the service. Because the total number of hydrants is the same as what currently exists the results can be compared with the presented solution. The proposed model reduces the total distance run to access the service, from 16,177 m to 13,560 m (16.17%), and the objective function (proportional to the cost) by 28.95%. © 2012 American Society of Civil Engineers.