Search

Evapotranspiration is an important parameter to evaluate soil water deficit and water use efficiency, especially at places with irregularly distributed precipitation.The aim of this study was to assess the daily actual evapotranspiration (ETa) estimated by the Thornthwaite and Mather soil water balance method adapted for crops (ThM) and by the dual Kc approach with the crop coefficients optimized from inversing modeling and by the adjustment procedure suggested in FAO-56. The models comparison and optimization were performed with actual evapotranspiration determined by the Bowen ratio – energy balance method (ETβ) for sugarcane at full canopy closure grown in Alagoas State, Northeastern Brazil. The objective function of the inverse problem was defined in terms of ETβ and ETa estimated by the ThM and dual Kc method by optimizing single crop coefficient (Kc) and the basal coefficient Kcb, respectively. Both optimized Kcand Kcbwere lower than the adjusted KcFAO56, with optimized Kconly 3% less than the Kc obtained experimentally. ETa estimated by ThM and dual Kc models with optimized crop coefficients (Kc = 1.05 or Kcb = 1.00) had similar high precision (r² >0.79) and accuracy (dm>0.93 and RMSE < 0.30 mm d-1), whereas using the coefficients derived from FAO 56 overestimated ETa in both models.

A critical component of water-resources management in the irrigated agriculture landscape, particularly those landscapes dependent on groundwater availability, is determining groundwater recharge rates from streams and other channels. In California, flows in many such channels are “controlled” by upstream reservoir releases to meet downstream urban, irrigation and environmental water requirements. Seepage volumes from these channels and how they might vary during controlled release periods is a key component of meeting downstream riparian and groundwater-pumping needs. Understanding annual seepage from streamflow channels is also important in developing water budgets as part of the management of groundwater resources under the Sustainable Groundwater Management Act (SGMA) in California. However, direct measurements of channel seepage rates are infrequent or unavailable, and these rates, or associated volumes, are most often only estimated. Here we describe direct point- and reach-scale field measurements of channel seepage rates in Lower Putah Creek (Solano County) and in distribution lateral channels of the Oakdale Irrigation District on the east side of the San Joaquin Valley (San Joaquin and Stanislaus counties). We measured overall average seepage rates of about 2 feet (610 mm) per day at both locations and determined how these rates varied spatially and temporally during the summer when channel flows are controlled for downstream requirements.

Evaluating the adequacy and efficiency of irrigation practices and identifying potential irrigation management improvements in agricultural watersheds require accurate estimates of water fl...

This study developed a cell-based daily soil water analysis model (CellSW) for evaluating agricultural drought and calculated an agricultural drought index called the &ldquo, Rainfall Effectiveness Index for Crop&rdquo, (REIC). The model analyzed a daily soil water balance based on crop types, growth stages, soils, and climate. It adopted the rasterized daily rainfall, daily evapotranspiration, crop coefficient (by crop growth stage), and root depth as input parameters, it also consecutively generated the daily surface layers of the water balance items in each cell, such as the consumptive use, effective rainfall, available soil water, and irrigation requirements. The model was applied in a test area in Illinois and Iowa, targeting corn and soybeans, the soil water balance was analyzed during the growing period from 2000 to 2018. The model calculated the seasonal REIC, defined as the ratio of supply quantity (effective rainfall) to demand quantity (crop evapotranspiration). In addition, the accumulated REIC values were estimated. The REIC was confirmed to accurately reflect drought situations in the relevant areas, based on comparisons with drought records. The cell-based model can be applied to different types of cultivated crops, growth stages, and soil conditions without spatial and temporal limitations, even in mixed farming.

Dune belts are crucial for the recharge of coastal aquifers. In spite of their hydrological relevance for the maintenance of precious natural wetland and wildlife environments and a range of other ecosystemservices, only limited knowledge of soil water dynamics in dune belts is currently available. This study presents soilwater balance components measured during one hydrological year using a high precision meteo-lysimeter with lower boundary control installed in a coastal dune belt under a dry subhumid climate in southern Spain close to the Atlantic Ocean. The site is equipped with a cylindrical lysimeter of 1 m2 surface and 1.50 m height (METER Group, Inc. USA) and a weighing resolution of 10 g, 2 SC650 soil moisture sensors (Campbell Scientific, Logan, UT) and 1 automatic meteorological station. The lower boundary condition at the bottom of the lysimeter is controlled at 1.4 m depth by a bidirectional peristaltic pump to maintain field conditions. Results show a recharge rate of 64% of the precipitation measured by the lysimeter. Diurnal oscillations of the measured upper boundary flow during days without rainfall represented vapor adsorption and real evaporation rates ranging between 0.3 and 0.4 mm/day and 0.4 and 0.6 mm/day, respectively throughout the whole year summing up an annual vapor adsorption of 77mm. The measured precipitation of the lysimeter exceeded pluviometer data by 13% as a result of vapor adsorption. The presented results provide a precise balance of soilwater components in a coastal dune belt including the relevant contribution of vapor flow., Unidad de Sevilla, Instituto Geológico y Minero de España, España, Departamento de Física Aplicada, Universidad de Córdoba, España, Centro Alameda del Obispo, Investigación y Formación Agraria y Pesquera, España, Instituto Geológico y Minero de España, España

Under arid conditions, where water availability is the limiting factor for plant survival, water balance models can be used to explain vegetation dynamics. [...]

Mediterranean oak savannas (known as dehesas in Spain) are exposed to numerous threats from natural and economic causes. A close monitoring of the use of water resources and the status of the vegetation in these ecosystems can be useful tools for maintaining the production of ecological services. This study explores the estimation of evapotranspiration (ET) and water stress over a dehesa by integrating remotely sensed data into a water balance using the FAO-56 approach (VI-ETo model). Special attention is paid to the different phenology and contribution to the system&rsquo, s hydrology of the two main canopy layers of the system (tree + grass). The results showed that the model accurately reproduced the dynamics of the water consumed by the vegetation, with RMSE of 0.47 mm day&minus, 1 and low biases for both, the whole system and the grass layer, when compared with flux tower measurements. The ET/ETo ratio helped to identify periods of water stress, confirmed for the grassland by measured soil water content. The modeling scheme and Sentinel-2 temporal resolution allowed the reproduction of fast and isolated ET pulses, important for understanding the hydrologic behavior of the system, confirming the adequacy of this sensor for monitoring grasslands water dynamics.

Over the past two decades, remote sensing has made possible the routine global monitoring of surface soil moisture. Regional agricultural drought monitoring is one of the most logical application areas for such monitoring. However, remote sensing alone provides soil moisture information for only the top few centimeters of the soil profile, while agricultural drought monitoring requires knowledge of the amount of water present in the entire root zone. The assimilation of remotely sensed soil moisture products into continuous soil water balance models provides a way of addressing this shortcoming. Here, we describe the assimilation of NASA's soil moisture active passive (SMAP) surface soil moisture data into the United States Department of Agriculture Foreign Agricultural Service (USDA FAS) Palmer model and assess the impact of SMAP on USDA FAS drought monitoring capabilities. The assimilation of SMAP is specifically designed to enhance the model skill and the USDA FAS drought capabilities by correcting for random errors inherent in its rainfall forcing data. The performance of this SMAP-based assimilation system is evaluated using two approaches. At global scale, the accuracy of the system is assessed by examining the lagged correlation agreement between soil moisture and the normalized difference vegetation index (NDVI). Additional regional-scale evaluation using in situ- based soil moisture estimates is carried out at seven of the SMAP core Cal/Val sites located in the USA. Both types of analysis demonstrate the value of assimilating SMAP into the USDA FAS Palmer model and its potential to enhance operational USDA FAS root-zone soil moisture information.

THREE-DIMENSIONAL WATER EXTRACTION IN THE ROOT ZONE OF DRIP-IRRIGATED TOMATO FRANCISCO AIRDESSON LIMA DO NASCIMENTO¹; ALISSON JADAVI PEREIRA DA SILA²; VALERIA ALMEIDA JATOBA³; ALLAN RADAX FREITAS CAMPOS4 E JILCÉLIO NUNES DE ALMEIDA³ 1- Doutorando em Engenharia Agrícola pela Universidade Federal do Recôncavo da Bahia (UFRB), Rua Rui Barbosa, 710, Centro, 44.380-000, Cruz das Almas, Bahia, Brasil, airdessonpai@hotmail.com; 2- Professor Doutor do Intituto Federal de Educação, Ciência e Tecnologia Baiano (IF Baiano), Campus Governador Mangabeira, Rua Waldemar Mascarenhas, 656, Centro, 44350-000, Gov. Mangabeira, Bahia, Brasil, alissonagr@gmail.com; 3- Licenciado(a) em Ciências Agrárias pelo Intituto Federal de Educação, Ciência e Tecnologia Baiano (IF Baiano), Campus Senhor do Bonfim, Estrada da Igara, s/n, Zona Rural, 48970-000, Senhor do Bonfim, Bahia, Brasil, valeriajatoba87@hotmail.com; 4- Doutor em Engenharia Agrícola pela Universidade Federal do Recôncavo da Bahia (URFB), Rua Rui Barbosa, 710, Centro, 44.380-000, Cruz das Almas, Bahia, Brasil, allanradax@hotmail.com. 1 ABSTRACT Soil water sensing is a common alternative for irrigation management. Due to the difficulty to determine the spatial-temporal variability of water extraction (WE) in the root zone of a crop it is still arbitrary the definition of number and position of water content sensors to be installed for irrigation management purposes. The main objectives of this work are to use Time Domain Reflectometry (TDR) to detail – in three-dimensions – WE in the root zone of tomato plants cultivated in covered and uncovered soil; and, to evaluate if there are differences in the values of tomato crop evapotranspiration (ET) determined through soil water balance (SWB) with one, two, three and four TDR probe monitoring profiles. The study was carried out under semiarid condition. Tomatoes were grown in the field and two drainage lysimeters were installed in the center of cultivation area. In one lysimeter the soil surface was maintained uncovered, while in the other the soil surface was covered with a black plastic canvas. Eight TDR probes were installed within each lysimeter for the three-dimensional monitoring of soil water content (SWC). WE was estimated with SWC data. It was found that WE in tomato root zone is more intense in regions of greater water availability in the soil, i.e, on wet wet bulb formed inside the soil. There are no differences in the estimation of tomato crop evapotranspiration through soil water balance varying the position of two-dimensional soil water content monitoring. However, when soil water balance is performed in three-dimensions there may be large differences in daily tomato crop evapotranspiration estimation compared to the two-dimensional soil water balance. Keywords: tomato, sensor placement, irrigation management. NASCIMENTO, F.A. L.; SILVA, A. J.P.; JATOBA, V.A.; CAMPOS, A.R.F.; ALMEIDA, J.N EXTRAÇÃO TRI-DIMENSIONAL DE ÁGUA NA ZONA RADICULAR DO TOMATEIRO IRRIGADO POR GOTEJAMENTO 2 RESUMO O sensoriamento de água no solo é uma comum alternativa para o manejo da irrigação. Devido à dificuldade em se determinar a variabilidade espaço-temporal da extração de água na zona radicular dos cultivos, ainda é arbitrária a definição do número e posicionamento de sensores de água no solo a serem instalados para fins de manejo de irrigação. Diante disso, objetivou-se com o referido trabalho utilizar a Reflectometria no Domínio do Tempo (TDR) para detalhar, em três dimensões, a extração de água pelo tomateiro em cultivo com solo coberto e descoberto, e verificar se existem diferenças nos valores de evapotranspiração da cultura determinados pelo balanço de água no solo com um, dois, três e quatro perfis de monitoramento. O trabalho foi conduzido em condição semiárida nas fases de floração e frutificação da cultura. Montou-se um sistema de aquisição de dados, composto por uma TDR 100 e um datalogger modelo CR 800 para leitura e armazenamento de dados do conteúdo de água no solo. Dois lisímetros de drenagem foram instalados no centro de uma área de cultivo, sendo um mantido com a superfície do solo coberto com lona plástica. Em cada lisímetro, foram distribuídas oito sondas de TDR de modo a formar quatro perfis de monitoramento na zona radicular do tomateiro. A extração de água da zona radicular do tomateiro é mais intensa na região de maior disponibilidade de água, especificamente, na região do bulbo molhado. Não há diferença nos valores de evapotranspiração do tomateiro estimado variando-se a posição do perfil bi-dimensional. Entratanto, ao se comparar valores diários de evapotranspiração do tomateiro estimado com balanço de água no solo realizado em duas e três-dimensões, verificou-se haver largas diferenças. Palavras-chave: tomate, extração de água no solo, manejo da irrigação.

Large-scale in situ soil moisture monitoring networks are becoming increasingly valuable research tools, but existing networks feature almost exclusive deployment of stations in grassland vegetation. These grassland soil moisture observations are unlikely to adequately represent the real soil moisture patterns in landscapes with intermixed land cover types. Here we demonstrate the severity of the problem for one particular landscape and introduce a flexible new method for solving the problem. The specific objectives of this study were (i) to compare root-zone soil moisture dynamics of two dominant vegetation types across Oklahoma, grassland (observed) and winter wheat cropland (simulated); (ii) to relate the soil moisture dynamics of grassland and cropland vegetation using an artificial neural network (ANN) as an observation operator; and (iii) to use the resulting ANN to estimate the soil moisture spatial patterns for a landscape of intermixed grassland and wheat cropland. Root-zone soil moisture was represented by plant available water (PAW) in the top 0.8 m of the soil profile. PAW under grassland was calculated from 18 years of soil moisture observations at 83 stations of the Oklahoma Mesonet, whereas PAW under winter wheat was simulated for the same 83 locations using a calibrated and validated soil water balance model. Then, we trained an ANN to reproduce the simulated PAW under winter wheat using only six inputs: day of the year, latitude and longitude, measured PAW under grassland, and percent sand and clay. The resulting ANN was used, along with grassland soil moisture observations, to estimate the detailed soil moisture pattern for a 9 × 9 km2 Soil Moisture Active Passive (SMAP) grid cell. The seasonal dynamics of root-zone PAW for grassland and winter wheat were strongly asynchronous, so grassland soil moisture observations rarely reflect cropland soil moisture conditions in the region. The simple ANN approach facilitated efficient and accurate prediction of the simulated PAW under winter wheat, RMSD = 21 mm and normalized RMSD = 0.17, using observed PAW under grassland as an input. This new method for estimating soil moisture under adjacent, contrasting land covers at a relatively low computational cost could be employed for any region and land cover pairing with training data available, and it may significantly enhance the applications of existing large-scale soil moisture monitoring networks.

Rainfall is low and unreliable in much of Australia's dryland cropping areas, requiring well-informed crop management for optimising yield and profit. Growing-season rainfall is usually supplemented by soil water during fallow periods preceding a crop. While rainfall is conveniently measured, the difficulty of measuring a soil's plant available water (PAW, mm) has led to using simulation models for estimating PAW. Here we developed a smartphone application (app) that simulates soil water balance by accessing weather, soil and crop data from databases and on-farm records. Predictions of PAW using the Howleaky modelling engine were compared with field measurements. Validation of the simulation engine across sites in Australian cropping areas showed good agreement between simulated and measured PAW. Errors in model estimates are compared with variability found within small fields. We conclude that estimating PAW for paddocks using a simulation model built in a smartphone app is a reliable and adaptable technology.

Soil water repellency is a common phenomenon which develops when surface soils become dry in summer and autumn. It is claimed that repellency is likely to result in a lower infiltration rate and a concomitant increase in surface runoff, particularly on slopes. This study quantifies the effect of water repellency on runoff from a series of small plots on a range of slopes (20° and 30°) and aspects (N, S and E) in a hilly landscape in the south-east of the North Island of New Zealand. The plots (1 m wide and 2 m long) were set up to capture runoff via a slotted PVC pipe and measure it using tipping bucket apparatus: at each of the slope/aspect locations there were duplicate plots. A meteorological station was also established at the site along with TDR probes to measure soil moisture down to 300 mm depth. When moist, the soil at the site had a very high infiltrability (>1.5 mm/min). On nine occasions, runoff was measured (ranging from 1 to 59% of rainfall) when the soil surface was dry and rainfall was intense (greater than 0.1 mm/min). However, during the two-year study period, this repellency-induced runoff equated to only 5% of the total rainfall. Furthermore, the infiltration rate of initially dry, repellent soil (ranging from 0.2 to 0.6 mm/min) partly recovered over a ten-minute period (0.6–1.0 mm/min) and, with sufficient rainfall, repellency completely disappeared within two days. The transitory nature of water repellency was confirmed in an experiment on large soil slabs conducted in the laboratory where repellency-induced runoff was observed to largely disappear over a period of 30 min. Overall, it is concluded that soil water repellency does not play a major role in the soil water balance of the hill country at the study site.

In arid and semiarid environments, focused infiltration of rain and snowmelt water under topographic depressions is an important mechanism of groundwater recharge. Quantifying the aggregated recharge from numerous small depressions is a major challenge in water resource management. Building on field-based investigations into the surface water–groundwater interaction of individual depressions and their catchments (i.e., uplands) in the Canadian Prairies, we have developed a simple water balance model to simulate groundwater recharge considering the hydrological coupling of a depression–upland system. The model is based on the Versatile Soil Moisture Budget (VSMB), which has been widely used in the Canadian Prairies to simulate soil moisture conditions. We evaluated the new model, VSMB Depression-Upland System (VSMB-DUS), using field data consisting of an artificial flooding experiment and long-term monitoring of a depression in Alberta, Canada. The model captured surface water level, soil moisture, and groundwater responses to the artificial flooding with reasonable accuracy and represented the interannual variability of recharge fluxes during a 5-yr period (2007–2011), including dry and wet years. Simulated annual recharge varied between 12 and 45 mm, and annual precipitation varied between 453 and 597 mm during the 5-yr period. The VSMB-DUS tends to over- or underestimate snowmelt runoff in individual years; however, simulated recharge was only slightly affected by the errors in snowmelt runoff estimation. Due to its computational efficiency and robust algorithms, the VSMB-DUS will provide a useful tool for estimating aggregated recharge in a large-scale model grid cell containing hundreds of depression-upland systems.

While simple crop and hydrological models are limited with respect to the number and accuracy of the processes they incorporate, complex models have high demand for data. Due to the limitations of both categories of models, there is a need for new agro-hydrological models that simulate both crop productivity and water availability in agricultural catchments, with low data and calibration requirements. This study aimed at developing a widely applicable parsimonious agro-hydrological model, AquaCrop-Hydro, which couples the AquaCrop crop water productivity model with a conceptual hydrological model. AquaCrop-Hydro, simulating crop productivity, the daily soil water balance and discharge at the catchment outlet, performed well for an agricultural catchment in Belgium. The model can be used to investigate the effect of agricultural management and environmental changes from field to catchment scale in support of sustainable water management in agricultural areas.

Methodologies based on earth observation remote sensing allow for a precise estimation of actual water requirements for irrigated crops across large areas. In spite of the many number of experiments using or analyzing the relationship between the basal crop coefficient (Kcb) and the soil adjusted vegetation index (SAVI) for maize, the development of new maize hybrid varieties with modifications related to canopy architecture suggest a possible change of the leaf area index (LAI) for maximum Kcb and its relationship with the SAVI or other vegetation indices. In addition, we noted a lack of analysis of these relationships for cultivated soybean. The objective of this paper is to analyze the Kcb, SAVI and LAI relationships in maize and soybean based on the non-linear relationships proposed by Choudhury et al. (1994). In addition, we propose a modification of the Choudhury et al. (1994) approach based on field-based experimental evidence of a minimum Kcb greater than 0. For sites with limited field data, we also analyze the utility of a simple linear regression based on the Kcb and SAVI values for bare soil and maximum Kcb values. The resulting Kcb-SAVI relationships are assimilated into a remote sensing based soil water balance model. The results of the model are analyzed in terms of irrigation requirements and crop evapotranspiration (ETa) for 11 growing seasons in two fields cultivated with irrigated and rain-fed maize and soybean in eastern Nebraska. Comparisons of measured and modelled ETa values indicate a good agreement, with RMSE lower than 0.7 mm d−1 for weekly averaged values. The comparison of actual irrigation applied and irrigation requirements indicate the central pivot systems could not supply adequate water in some growing seasons with higher demands.

Under the present study estimation of high resolution soil moisture (SM) under Pan India mode using simple water balance method and from satellite data has been explored. It aims at the simple calculation of soil moisture followed by verification with ground truth data of SM on spatial and temporal scale (WC) as climatic input. The model has been verified for winter (January-February), pre-monsoon (March-May), monsoon (June-September) and post-monsoon (October-December) seasons of year 2013. The comparison of model estimates with the in-situ data from 17 ground stations (for 396 paired datasets) over different seasons produced a better correlation coefficient varying from 0.46 to 0.60. The spatial comparison of SM estimated from model and satellite SM for the monsoon season shows a greater degree of coherence over most parts of India. Model derived weekly gridded SM combined with higher resolution satellite SM could use simple formulation and minimum inputs in conjunction with geographic information system (GIS). The SM is calculated on weekly basis and using gridded rainfall, potential evapotranspiration (PET) and field capacity (FC) and wilting point be used for better accuracy of the proposed block level agrometadvisory services.

An accurate assessment of soil water balance components (SWBCs) is necessary for improving irrigation strategies in any water-limited environment. However, quantitative information of SWBCs is usually challenging to obtain, because none of the components (i.e., irrigation, drainage, and evapotranspiration) can be easily measured under actual conditions. Soil moisture is a variable that integrates the water balance components of land surface hydrology, and the evolution of soil moisture is assumed to contain the memory of antecedent hydrologic fluxes, and thus can be used to determine SWBCs from a hydrologic balance. A database of soil moisture measurements from six experimental plots with different treatments in the middle Heihe River Basin of China was used to test the potential of a soil moisture database in estimating the SWBCs. We first compared the hydrophysical properties of the soils in these plots, such as vertical saturated hydraulic conductivity (Ks) and soil water retention features, for supporting the SWBC estimations. Then we determined evapotranspiration and other SWBCs through a method that combined the soil water balance method and the inverse Richards equation (a model of unsaturated soil water flow based on the Richards equation). To test the accuracy of our estimation, we used both indirect methods (such as power consumption of the pumping irrigation well, and published SWBCs values at nearby sites), and the water balance equation technique to verify the estimated SWBCs values, all of which showed a good reliability of our estimation method. Finally, the uncertainties of the proposed methods were analyzed to evaluate the systematic error of the SWBC estimation and any restrictions on its application. The results showed significant variances among the film-mulched plots in both the cumulative irrigation volumes (652.1~ 867.3 mm) and deep drainages (170.7~364.7 mm). Moreover, the unmulched plot had remarkably higher values in both cumulative irrigation volumes (1186.5 mm) and deep drainages (651.8 mm) compared with the mulched plots. Obvious correlation existed between the volume of irrigation and that of drained water. However, the ET demands for all the plots behaved pretty much the same, with the cumulative ET values ranging between 489.1 and 561.9 mm for the different treatments in 2016, suggesting that the superfluous irrigation amounts had limited influence on the accumulated ET throughout the growing season because of the poor water-holding capacity of the sandy soil. This work confirmed that relatively reasonable estimations of the SWBCs in coarse-textured sandy soils can be derived by using soil moisture measurements; the proposed methods provided a reliable solution over the entire growing season and showed a great potential for identifying appropriate irrigation amounts and frequencies, and thus a move toward sustainable water resources management, even under traditional surface irrigation conditions.

© 2020 by the authors., Arid and semi-arid ecosystems are characterized by patchy vegetation and variable resource availability. The interplant spaces of these ecosystems are very often covered by cyanobacteria-dominated biocrusts, which are the primary colonizers of terrestrial ecosystems and key in facilitating the succession of other biocrust organisms and plants. Cyanobacterial biocrusts regulate the horizontal and vertical fluxes of water, carbon and nutrients into and from the soil and play crucial hydrological, geomorphological and ecological roles in these ecosystems. In this paper, we analyze the influence of cyanobacterial biocrusts on water balance components (infiltration-runoff, evaporation, soil moisture and non-rainfall water inputs (NRWIs)) in representative semiarid ecosystems in southeastern Spain. The influence of cyanobacterial biocrusts, in two stages of their development, on runoff-infiltration was studied by rainfall simulation and in field plots under natural rainfall at different spatial scales. Results showed that cover, exopolysaccharide content, roughness, organic carbon, total nitrogen, available water holding capacity, aggregate stability, and other properties increased with the development of the cyanobacterial biocrust. Due to the effects on these soil properties, runoff generation was lower in well-developed than in incipient-cyanobacterial biocrusts under both simulated and natural rainfall and on different spatial scales. Runoff yield decreased at coarser spatial scales due to re-infiltration along the hillslope, thus decreasing hydrological connectivity. Soil moisture monitoring at 0.03 m depth revealed higher moisture content and slower soil water loss in plots covered by cyanobacterial biocrusts compared to bare soils. Non-rainfall water inputs were also higher under well-developed cyanobacterial biocrusts than in bare soils. Disturbance of cyanobacterial biocrusts seriously affected the water balance by increasing runoff, decreasing soil moisture and accelerating soil water loss, at the same time that led to a very significant increase in sediment yield. The recovery of biocrust cover after disturbance can be relatively fast, but its growth rate is strongly conditioned by microclimate. The results of this paper show the important influence of cyanobacterial biocrust in modulating the different processes supporting the capacity of these ecosystems to provide key services such as water regulation or erosion control, and also the important impacts of their anthropic disturbance., This work has been supported by several research projects: REBIOARID (RTI2018-101921-B-I00), DINCOS (CGL2016-78075-P) projects, founded by the Spanish National Plan for Research and the European Union ERDF and the BIOCOST project Supported by Biodiversity Foundation of the Ministry for the Ecological Transition., Publisher’s version

Posavina region represents the area with the most favorable natural conditions for agricultural production in Croatia and Bosnia and Herzegovina. Increase in the air temperature and changes in the amount of rainfall results in changes in evapotranspiration and the values of main water balance elements indicating the need for a precise determination of the current and future state of basic water balance elements, such as soil moisture deficit and the amount of runoff. Linear regression was applied to determine soil water balance response to climate change in Posavina region. The air temperature, precipitation, reference evapotranspiration and water balance components: actual evapotranspiration, total runoff, soil moisture deficit and amount of snow trends were analyzed. Monthly weather data from 4 weather stations, two in Croatia: Slavonski Brod and Gradište ; and two in Bosnia and Herzegovina: Doboj and Gradačac, for the time period of 58 years (1961–2018) were used. The results obtained show increasing trends in annual air temperature (0.032 °C–0.057 °C year−1), sum of precipitation (1.424 mm–2.317 mm year−1), reference evapotranspiration (0.462 mm–4.640 mm year−1), actual evapotranspiration (0.019 mm– 2.190 mm year−1), soil moisture deficit (0.443 mm–2.672 mm year−1) and total runoff (0.286– 2.46 9 mm year−1) series and decreasing trend in the annual amount of snow (0.676–1.664 mm year−1). Results obtained are showing an urgent need to start with climate change adaptation measures and actions to combat the negative impact of climate change in the Posavina region.

As an important component of the water budget, quantifying actual crop evapotranspiration (ET) will enable better planning, management, and allocation of the water resources. However, accurate ET measurement has always been a challenging task in agricultural water management. In the upper Midwest, where subsurface drainage is a common practice due to the shallow ground water depth and heavy clayey soil, ET measurement using traditional ground-based methods is more difficult. In this study, ET was measured using the eddy covariance (EC), Bowen ratio-energy balance (BREB), and soil water balance (SWB) methods during the 2018 corn growing season, and the results of the three methods were compared. To close the energy balance for the EC system, the residual method was used. For the SWB method, capillary rise was included in the ET estimation and was calculated using the measured soil water potential. The change of soil water content for ET estimation using the SWB method was calculated in four different ways, including daily average, 24:00&ndash, 2:00 average, 24:00&ndash, 4:00 average, and 4:00 measurement. Through the growing season, six observation periods (OPs) with no rainfall or minimal rainfall events were selected for comparisons among the three methods. The estimated latent heat flux (LE) by the EC system using the residual method showed a 29% overestimation compared to LE determined by the BREB system for the entire growing season. After excluding data taken in May and October, LE determined by the EC system was only 10% higher, indicating that the main difference between the two systems occurred during the early and late of the growing season. By considering all six OPs, a 6%&ndash, 22% LE difference between the EC and the BREB systems was observed. Except during the early growing and late harvest seasons, both systems agreed well in LE estimation. The SWB method using the average soil water contents between 24:00 and 2:00 time period to calculate the daily capillary rise produced the best statistical fit when compared to the ET estimated by the BREB, with a root-mean-square error of 1.15. Therefore, measuring ET using the capillary rise from a shallow water table between 24:00 and 2:00 could improve the performance of the SWB methodology for ET measurement.

The success of an irrigation decision support system (DSS) much depends on the reliability of the information provided to farmers. Remote sensing data can expectably help validate that information at the field scale. In this study, the MOHID-Land model, the core engine of the IrrigaSys DSS, was used to simulate the soil water balance in an irrigated vineyard located in southern Portugal during three growing seasons. Modeled actual basal crop coefficients and transpiration rates were then compared with the corresponding estimates derived from the normalized difference vegetation index (NDVI) computed from Sentinel-2 imagery. On one hand, the hydrological model was able to successfully estimate the soil water balance during the monitored seasons, exposing the need for improved irrigation schedules to minimize percolation losses. On the other hand, remote sensing products found correspondence with model outputs despite the conceptual differences between both approaches. With the necessary precautions, those products can be used to complement the information provided to farmers for irrigation of vine crop, further contributing to the regular validation of model estimates in the absence of field datasets info:eu-repo/semantics/publishedVersion

Summary Knowing the components of a soil water balance—for example, evapotranspiration, soil water content, and precipitation—is the basis for agricultural water management. Weighing lysimeters and soil water sensors are commonly used to quantify these components. Data can be used to validate common models to estimate evapotranspiration based on meteorological data, for instance. As every measurement device has its own characteristics, it is helpful to assess and improve the performance of a system to obtain best possible data. Recent developments in the processing of lysimeter data allow determining both evapotranspiration and precipitation directly from lysimeter data. Resulting datasets are characterized by a proper accuracy, completeness, and a high temporal resolution. Soil water sensors usually measure a physical property that is related to soil water content or matric potential via a specific calibration function. Hence, measurement accuracy depends not only on this calibration but also on basic physical principles and material properties. Knowing the performance of a device is, therefore, essential for the selection of an adequate sensor arrangement and truthful data interpretation. Advanced soil water monitoring sites combine different sensor types that are integrated into a wireless network to enable real-time data availability and provide a basis for large-scale monitoring.

25 Pags.- 6 Figs.- 2 Tabls. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774, Accumulated daily crop evapotranspiration (ETc) generally provides good estimates of cumulative soil water depletion between irrigation of well drained soils. If the canopy is wet due to fog, dew, or light rainfall, however, energy contribution to surface evaporation will reduce transpiration and hence soil water losses. When surface evaporation occurs, the ETc overestimates the soil water depletion by an amount approximately equal to the surface water evaporation. Moratiel et al. (2013) proposed a method to estimate the contribution of surface water to ETc based on the time of canopy drying. The first method assessment was done with California data, and this evaluation was conducted in the Ebro basin, Spain, to appraise the method in a higher latitude in area with a somewhat different climate. Differences between the California and Spain corrected models were less than 10% and depended mainly on the time of canopy drying. The comparison showed that the model is robust and useful to estimate the fraction (F) of ETc coming from the soil under dew, light rainfall, and fog conditions., Thanks are due to Ministry of Agriculture, Food and Environment for facilitating data collection.

The European Space Agency Climate Change Initiative Soil Moisture (ESA CCI SM) product provides soil moisture estimates from radar satellite data with a daily temporal resolution. Despite validation exercises with ground data that have been performed since the product&rsquo, s launch, SM has not yet been consistently related to soil water storage, which is a key step for its application for prediction purposes. This study aimed to analyse the relationship between soil water storage (S), which was obtained from soil water balance computations with ground meteorological data, and soil moisture, which was obtained from radar data, as affected by soil water storage capacity (Smax). As a case study, a 14-year monthly series of soil water storage, produced via soil water balance computations using ground meteorological data from northeast Portugal and Smax from 25 mm to 150 mm, were matched with the corresponding monthly averaged SM product. Linear (I) and logistic (II) regression models relating S with SM were compared. Model performance (r2 in the 0.8&ndash, 0.9 range) varied non-monotonically with Smax, with it being the highest at an Smax of 50 mm. The logistic model (II) performed better than the linear model (I) in the lower range of Smax. Improvements in model performance obtained with segregation of the data series in two subsets, representing soil water recharge and depletion phases throughout the year, outlined the hysteresis in the relationship between S and SM.

Soil water-vegetation interactions have been a research topic for decades. Landscape patterns can be shaped by soil water availability, and in reverse. The effects of subsurface flow on the soil water – vegetation interactions are relatively less studied than the surface flow, especially in the semiarid region. This work is focused on how the larch (Larix principis-rupprechtti) interacted with soil water, and how the convex pattern of the larch was formed along the stony soil slope in the semiarid Loess Plateau, northwest China. The soil water balance equation in Soil Water Assessment Tool (SWAT) was modified to include subsurface flow exchange between two adjacent hydrologic response units (HRUs). The slope was then delineated into adjacent HRUs to understand the hydrologic and ecological processes inside the slope. The modified SWAT model on the slope was calibrated and validated by the field data. The model was forced by a 55-year meteorological data series to investigate the larch-soil water interactions and the formation of the convex distribution pattern over long term. It is found that the subsurface flow has shaped the convex distribution of vegetation LAI along the slope. The subsurface flow occurs due to relatively high permeability of the stony soil, and it affects the heterogeneities of soil water availability through the soil water storage capacity. The concave spatial pattern of the soil water stress determines the vegetation growth along the slope in this semiarid region. These understandings provide new knowledge about the influences of hydrological processes on vegetation distribution patterns along a slope, which is useful in vegetation management under similar conditions.

Future extreme precipitation (EP, daily rainfall amount over certain thresholds) is projected to increase with global climate change; however, its effect on groundwater recharge has not been fully explored. This study specifically investigates the spatiotemporal dynamics of groundwater recharge and the effects of extreme precipitation (daily rainfall amount over the 95th percentile, which is tagged by ranking the percentiles in each season for a base period) on groundwater recharge from 1950 to 2010 over the Northern High Plains (NHP) Aquifer using the Soil Water Balance Model. The results show that groundwater recharge significantly (p

Evaluation of the monthly soil water balance (SWB) provides a tool for understanding and predicting the effects of seasonal and long-term changes in soil water conditions within many geotechnical problems. In this paper, two applications of the SWB approach in the pyroclastic partially saturated soils are shown. Firstly, rainfall, evapotranspiration, water storage measured or estimated at the experimental site in Monteforte Irpino (in Southern Italy) are shown. Secondly, rainfall, infiltration, actual evapotranspiration and water storage measured by data provided by a physical model are shown. In the both cases, data are reported over two years (2010-2012). The physical model was constituted by a wooden tank filled with reconstituted silty pyroclastic soil taken from experimental site at Monteforte Irpino (AV) and it was exposed to the atmosphere at a site in Napoli. Comparison between soil hydraulic behaviours observed is discussed and the scale effects on the estimation of the SWB are analysed, treating with practical implications. From the results, it is clear that similar trends in SWB and the same value of suction over wet season (10 kPa) can be observed at both the scales in spite of differences in meteorological conditions and hydraulic properties of soils exposed to atmosphere.

In order to figure out the future drought characteristics of the Jeonju plains, the major crop production area in Korea, daily agricultural drought indexes based on soil water balance were calculated for the relevant 12.5 km by 12.5 km grid cell using the weather data generated by the RCP8.5 climate scenario during 1951-2100. The calculations were grouped into five climatological normal years, the past (1951-1980), the present (1981-2010), and the three futures (2011-2040, 2041-2070, and 2071-2100). Results showed that the soil moisture conditions in early spring, worst for both the past and present normal years, will ameliorate gradually in the future and the crop water stress in spring season was projected to become negligible by the end of this century. Furthermore, the drought frequency in early spring was projected to diminish, resulting in rare occurrence of spring drought by that time. However, the result also showed that the soil moisture conditions during the summer season (when most crops grow in Jeonju plain) will deteriorate and the drought incidence will be more frequent than in the past or present period.

Climate change forecasts in a semiarid region are of much interest to academics, managers and governments. A significant decrease in annual precipitation and an increase in mean annual air temperature are expected; consequently, changes in the soil water balance and groundwater recharge to aquifers are expected as a response to climate change forecasts. In this context, our study aimed to assess the impact of climate changes on the soil water balance and natural groundwater recharge in a semiarid area (Ventós-Castellar aquifer, SE, Spain). To this end, we selected Global Climate Model HadCM3 after comparing it with two other models (ECHAM4 and CGCM2). The HadCM3 model climate data (air temperature and precipitation in two emission scenarios: A2-high and B2-low; 2011–2099) were coupled to a HYDROBAL hydrological model to determine the soil water balance. The HYDROBAL model results showed that climate change will have a significant impact on the soil water balance in the study area, especially on groundwater recharge during the latter period. In both the A2-high and B2-low scenarios, the selected years to run the HYDROBAL model showed a decrease in water balance components (precipitation, actual evapotranspiration, aquifer recharge and runoff) in relation to the baseline period (1961–1990). Over the projected period (2011–2099), we expect fewer rainfall events (>15 mm), which promote aquifer recharge, longer dry summer seasons and, consequently, reduced average annual recharge that ranged from 3% to 17%; 10–49 mm, if compared to the baseline period. The methodology developed in the present study can be beneficial for assessing the impact of predicted climate change on groundwater recharge, and can help managers and planners to devise strategies for the efficient use and conservation of freshwater resources. This research has been supported by the United Nations Educational, Scientific and Cultural Organization – France (IGCP-513), the European Commission – Belgium (PRACTICE project), the Spanish Government through the Ministry of Economy and Competitiveness – Spain (ECOBAL Project, CGL2011-30531-C03-01 and SURVIVE project, CGL 2011-30531-C02-02), the Consolider programme INGENIO 2010 (GRACCIE Project, CSD2007-00067), and the Generalitat Valenciana – Spain (FEEDBACKS-PROMETEO; ACOMP/2010/272 and GV07/143).

RESUMO O conceito de pegada hídrica tem tido bastante interesse atualmente haja vista que a água doce é um recurso global utilizado em todos os ramos de atividades e pode ser fundamental para ajudar a compreender como as atividades e os produtos estão relacionados com a escassez de água. O objetivo deste estudo é comparar as medições da pegada hídrica da cana-de-açúcar derivadas pelo método tradicional utilizado na sua estimativa usando o balanço hídrico completo no solo em condições de campo. O experimento de campo foi realizado na Fazenda Capim II, localizada no litoral do estado da Paraíba, Brasil, no período de outubro de 2009 a agosto de 2010 com cana-de-açúcar, cultivar RB 92 579. Os resultados evidenciaram que os valores da pegada hídrica verde e cinza diminuem à medida que há acréscimo na lâmina de irrigação. Inversamente, os valores da pegada hídrica azul aumentam sempre que há incremento na lâmina de irrigação. A pegada hídrica da cana-de-açúcar obtida com base no modelo CROPWAT, superestima os valores da pegada hídrica verde e azul e subestima os valores da pegada hídrica cinza, obtidos com base no balanço hídrico do solo. ABSTRACT The water footprint concept has gained interest because the freshwater is a global resource utilized in all activities and can be fundamental in helping to understand how activities and products are related to water scarcity. The purpose of this study is to compare the sugarcane water footprint measurements derived by the traditional method used for its estimation and using the complete water balance in the soil under field conditions. The field experiment was carried out at the Capim II farm located in the coastal area of state of Paraiba, Brazil, during the period from October 2009 to August 2010 with sugarcane. The results indicated that the green and gray water footprint values decrease as there is an increase in irrigation depth. Inversely, the blue water footprint values increase as there is an increase in irrigation depth. The sugarcane water footprint based on the CROPWAT model overestimates green and blue water footprint values and underestimates the gray water footprint values obtained from the soil water balance.

Las inundaciones y sequías son una constante en la Región Pampeana (Argentina). Casi todos los años uno de estos eventos hidrológicos extremos tiene lugar y, a veces, ambos. La evolución temporal del exceso de agua en el suelo, durante sesenta años se analiza en nueve estaciones meteorológicas localizadas en importantes áreas cuyos usos del suelo tienen impacto económico y social. Ellas se ubican en las provincias de Córdoba, Santa Fe, Entre Ríos, La Pampa y Buenos Aires. Los datos meteorológicos diarios fueron provistos por Servicio Meteorológico Nacional para el período 1951- 2010. El modelo de balance de agua en el suelo fue el utilizado por Forte Lay et al. que está basado en el de Thornthwaite-Mather y la evapotranspiración diaria de referencia normal media fue estimada con la fórmula de Penman-Monteith. En el presente trabajo al parámetro exceso de agua en el suelo se lo utiliza como indicador del riesgo de inundación. La metodología Makesens se usó para el análisis estadístico, el mismo se basa en el test no paramétrico de Mann-Kendall para el estudio de la tendencia y el método no paramétrico Sen para su magnitud. Todas las estaciones analizadas mostraron diferente evolución del exceso de agua en el suelo y experimentaron riesgo de inundación en algún momento del período estudiado., Floods are a constant in the central eastern region of Argentina as well as droughts. Almost every year, one of these two extreme hydrologic events takes place and sometimes, both of them. The temporal evolution of soil water surplus, during sixty years, is studied in nine meteorological stations. These are located in important areas whose land uses have economic and social impact. They are localized in the provinces of Córdoba, Santa Fe, Entre Ríos province, La Pampa and Buenos Aires. Daily meteorological data were provided by the National Meteorological Service and the period considered was 1951-2010. Soil water balance was performed according the model used Forte Lay et al. which is based on Thornthwaite-Mather method and the normal daily mean reference evapotranspiration was estimated by the Penman-Monteith formula. In the present paper the parameter soil water surplus is used as an index of flood risk. Makesens methodology was used for the statistical analysis; this is based in non parametric test Mann-Kendall for the trend study and the non parametric method Sen for the magnitude. All the analyzed stations showed different evolution of soil water surplus and have experienced flood risk in some moment of the studied period., Facultad de Humanidades y Ciencias de la Educación

© 2017 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (August 2017) in accordance with the publisher’s archiving policy., Coupled water and energy balance models have become increasingly popular for estimating groundwater recharge, because of the integration of energy and water balances and sometimes carbon balance. The additional balances are thought to constrain the water balance and as a result should help reduce the uncertainty of groundwater recharge. However, these models usually have a large number of parameters. The uncertainty of these parameters may result in a large uncertainty in groundwater recharge estimates. This study aims to assess the potential uncertainty of groundwater recharge estimated from a widely used water and energy model. It is largely based on annual pasture vegetation in the lower part of the Campaspe catchment in southeast Australia. A Monte Carlo analysis method was employed to examine potential uncertainties introduced by different types of errors. The results show that for a mean rainfall of 398 mm/y and using a particular set of pedotransfer functions for deriving soil hydraulic parameters, the estimated recharge ranged from 7 to 144 mm/y due to the uncertainty in vegetation parameters. This upper bound of the recharge range increased to 236 mm/y when using different sets of pedotransfer functions. Through several synthetic test cases, this study shows that soil moisture time series may not offer much help for reducing recharge uncertainty, whereas evapotranspiration time series are able to reduce recharge uncertainty by more than 50%. The reduction in recharge uncertainty steadily improves as the uncertainty in observations reduces.

Integrating micro-flood irrigation with in-field rainwater harvesting (IRWH) was proposed and experiments were conducted in the 2007–2008 production season at Parady's Experimental Farm of the University of the Free State, South Africa. Three water regimes, dryland (DL), supplemental (SPI), and full irrigation (FI), were tested with 1, 2, and 3 m runoff strip width (RSW) to determine their effects on soil water balance components for the integrated IRWH. Four blocks with nine subplots were prepared for the 3 × 3 split plot factorial experimental design. Plots were 30 m long with a standard 1 m width. Site specific data were used to estimate rainfall-runoff and deep drainage functions. Soil water content (SWC) was measured with a Neutron water meter. Evapo-transpiration (ET) was partitioned into evaporation and transpiration using a β parameter. Deep drainage was the least significantly affected. Rainfalls not less than 24 mm had significantly higher gains on change in SWC for the 2 m and 3 m RSW. During d...

The approach combines the basal crop coefficient ( K cb ) derived from vegetation indices (VI s ) with the daily soil water balance, as proposed in the FAO-56 paper, to estimate daily crop evapotranspiration (ET c ) rates of orange trees. The reliability of the approach to detect water stress was also assessed. VI s were simultaneously retrieved from Worldview 2 imagery and hyper-spectral data collected in the field for comparison. ET c estimated were analysed at the light of independent measurements of the same fluxes by an eddy covariance (EC) system located in the study area. The soil water depletion in the root zone of the crop simulated by the model was also validated by using an in situ soil water monitoring. Average overestimate of daily ET c of 6% was obtained from the proposed approach with respect to EC measurements, evidencing a quite satisfactory agreement between data. The model also detected several periods of light stress for the crop under study, corresponding to an increase of the root zone water deficit matching quite well the in situ soil water monitoring. The overall outcomes of this study showed that the FAO-56 approach with remote sensing-derived basal crop coefficient can have the potential to be applied for estimating crop water requirements and enhancing water management strategies in agricultural contexts.

Soil moisture is important for many applications, but its measurements are lacking globally and even regionally. The Walnut Gulch Experimental Watershed (WGEW) in southeastern Arizona has measured near-surface 5-cm soil moisture with 19 in situ probes since 2002 within its 150 km2 area. Using various criteria to identify erroneous data, it is found that in any given period from 1 July to 30 September from 2002 to 2011, 13–17 of these probes were producing reasonable data, and this is sufficient to estimate area-averaged seasonal soil moisture. A soil water balance model is then developed using rainfall as its only input to spatially extrapolate soil moisture estimates to the 88 rain gauges located within the watershed and to extend the measurement period to 56 years. The model is calibrated from 2002 to 2011 so that the daily in situ and modeled soil moisture time series have a high average correlation of 0.89 and a root-mean-square deviation of 0.032 m3 m−3. By interpolating modeled soil moisture from the 88 rain gauges to a 100-m gridded domain over WGEW, it is found that spatial variability often increases when 88 (rather than 13–17) estimates are taken. While no trend in the spatial average surface soil moisture is found, large variability in the spatial average soil moisture from 1 July to 30 September is observed from year to year, ranging from 0.05 to 0.09 m3 m−3. In addition to spatiotemporal analysis of WGEW, this gridded soil moisture product from 1956 to 2011 can be used for validation of satellite-based and reanalysis products and land surface models.