Comparison of Crop Water Use Estimation Methodologies in Irrigated Crops

As increasing drought events limit water resources available for irrigation, farmers and other water users are looking for ways to monitor how much water crops use over a growing season. The amount of water used by crops over time is the evapotranspiration (ET) rate. This study compares different methods for ET estimation to recommend methods to water users based on their accuracy, efficiency, and accessibility. Each method was used to estimate ET for sprinkler-irrigated corn and alfalfa fields in Modena, UT over the 2021 growing season. The Soil Moisture based ET (SMET) method was used to estimate ET based on daily changes in the soil water content. The OpenET web platform [www.openetdata.org] and the OpenET Application Programming Interface (API) were used to retrieve ET estimates based on imagery from the Landsat satellite. ET estimates for the area were also retrieved from a Utah Department of Natural Resources (DNR) report. The eddy covariance (EC) method is accepted as the standard for estimating ET and served as the standard for the comparison of all other methods. Results indicate that while all methods underestimate ET, the SMET method agrees most closely to the EC method. Further analysis of the OpenET and Utah DNR methods is required to fully explain the reasons for the apparent ET estimation discrepancies. This study also highlights the advantages and limitations of each method

Measurement and modeling of soil moisture for irrigation management

Increasing strain on freshwater resources due to population growths, climate change, and excessive depletion of water resources necessitates research in maximizing beneficial water use in agriculture regions. Smart technologies have a vital role to play in achieving this goal. Soil moisture sensors (SMS) have been well-recognized as effective smart technologies due to their proven ability to deliver efficient and practical irrigation management. However, the adoption of SMS by agricultural producers has remained limited over the last 20 years. There is an urgent need to investigate the barriers behind the low adoption of SMS and conduct applied research projects to demonstrate the advantages of SMS utilization. The objectives of this study were to: (1) conduct a Strengths, Weaknesses, Opportunities, Threats (SWOT) analysis on published literature related to SMS applications in irrigation management to identify shortcomings and potentials; (2) assess the performance of commercially available soil moisture sensors in irrigated fields of Oklahoma; and, (3) investigate the performance of computer models in estimating soil moisture dynamics and quantifying irrigation fluxes under field conditions. The SWOT analysis revealed the lack of adequate local field studies in determining SMS accuracy, reliability, and affordability under variable soil and climatic conditions. The accuracy of five commercially available SMS was determined under variable soil texture and salinity in Oklahoma. The evaluation of moisture thresholds obtained from different methods showed the effects of threshold variability on practical irrigation management. Using a combination of measurement and modeling techniques, water fluxes in an agricultural watershed provided valuable information on actual irrigation practices employed by producers. This methodology can be applied to other irrigated areas to evaluate irrigation management strategies

The impact of soil water distribution on root development and root water uptake of winter wheat

Root water uptake (RWU) is a key process in the root zone that determines water movement from the soil into roots and transport to the atmosphere via plant leaves. Different RWU models were developed with different assumptions and parameters but the description of this process and its parameterization remain challenging in soil hydrology. Due to the difficulty to obtain root development and soil states in undisturbed soils, dynamic root distributions and a physically based concept to describe water uptake from soil profiles with vertical variations in soil water availability are often not taken into consideration. The simulated RWU is rarely evaluated by measured transpiration for field conditions. This study aims at 1) introducing two minirhizotron (MR) facilities that were installed in two types of soils with different water treatments for monitoring dynamics of root and soil moisture in situ, 2) parameterizing RWU models that use different concepts and investigating the difference in RWU patterns and possible links, 3) exploring the effect of soil water availability on root development and RWU that were estimated by different RWU models, and evaluating the estimated RWU by measured transpiration. Winter wheat was considered in this study. Two MR facilities were constructed in two different soils (stony vs. silty) to monitor root growth and root zone processes. Each facility was established with three subplots: sheltered, rainfed, and irrigated. Root dynamics were observed in 7-m-long rhizotubes that were installed horizontally at 10, 20, 40, 60, 80, and 120 cm depth. Time domain reflectometer (TDR) probes, tensiometers, and matrix potential sensors were installed at those six depths to measure soil water content and water potential. The measurements served as input for inversely estimating soil and root-system related parameters of three RWU models: Feddes (without compensation), Feddes-Jarvis (with compensation, FJ), and Couvreur (physically based model with compensation that have been implemented in Hydrus-1D, C). Sap flow was monitored in each plot of the two soils. Measurements in the rhizotron facilities demonstrated that soil water content, root density, and crop biomass of winter wheat were higher in the silty than in the stony soil, in which plant and root growth were obviously affected by water treatments and soil types. Using the data from the sheltered plot of the stony soil, the three models predicted soil moisture equally well and the soil hydraulic parameters optimized by the models with compensation were comparable. The obtained RWU parameters of the FJ model and root hydraulic parameters for winter wheat were consistent with data reported in the literature. The FJ and C models simulated similar root-system scale stress functions that link total RWU to the effective root zone water potential. The root-system related parameters of the C model could be constrained but not those of the FJ model. When broadening the model parameterization and simulations to different soils and water treatments, the soil hydraulic parameters could be well identified by the FJ and C models. Patterns of crop and root development differed in the plots of the two soils, which resulted in different RWU due to different soil water availability. The FJ and C models simulated similar RWU which was the lowest in the sheltered plot of the stony soil where RWU was also lower than the potential RWU. In the silty soil, RWU was equal to the potential uptake for all treatments. The C model predicted the ratios of the transpiration fluxes in the two soils slightly better than the FJ model. The variation of simulated RWU between the different plots agreed well with measured sap flow but with a constant offset which needs further study.Der Einfluss der Bodenwasserverteilung auf die Entwicklung und die Wasseraufnahme der Wurzeln von Winterweizen Die Wurzelwasseraufnahme (WWA) kontrolliert den Wassertransport vom Boden über die Pflanze in die Atmosphäre. Verschiedene mathematische Modelle, die sich in ihrer Komplexität und ihren Parameter unterscheiden, erklären die WWA; doch nach wie vor ist die Beschreibung dieses Prozesses eine Herausforderung in der Bodenhydrologie. Die Messung der Wurzelentwicklung im ungestörten Boden ist kompliziert, daher wird die dynamische Verteilung von Wurzeln und deren Wasseraufnahme häufig nicht beachtet. Ferner werden simulierte WWA selten mit Transpirationsmessungen verglichen. Die vorliegende Studie hat zum Ziel 1) zwei Minirhizotron Anlagen (MR) zu beschreiben, welche zur in-situ-Erfassung der dynamischen Wurzelentwicklung in zwei verschiedenen Böden installiert wurden, 2) drei verschiedene Modelle zur WWA zu parametrisieren, um Unterschiede in den Mustern der Wasseraufnahme herauszufinden, 3) den Effekt von Bodenwasserverfügbarkeit auf die Wurzelentwicklung zu untersuchen und die abgeschätzte WWA mit Xylemflussmesswerten zu bewerten. Die Modellansätze und Methoden sind allgemeingültig; in dieser Studie wurde Winterweizen betrachtet. Die MR Anlagen wurden auf zwei Böden (steinig vs. schluffig) zur Betrachtung des Wurzelwachstums und anderer Prozesse der Wurzelzone konstruiert. Beide Anlagen wurden dreigeteilt: überdacht, beregnet und bewässert. Betrachtungen der Wurzeldynamiken erfolgten in sieben Meter langen Plexiglasröhren, horizontal installiert in 10, 20, 40, 60, 80 und 120 cm Tiefe. In diesen Tiefen wurden auch mittels Sensoren Wasserpotential, Bodenfeuchte und -temperatur gemessen. Diese Daten waren Input für die Schätzung der von Boden- und Wurzelsystem abhängigen Parameter von drei Modellen zur WWA: Feddes (F), Feddes-Jarvis (FJ) und Couvreur (C), implementiert in Hydrus-1D. Die Simulationen wurden mit lokalen Xylemflussmessungen verglichen. Die MR Messungen zeigten, dass Bodenwassergehalt, Wurzeldichte und Pflanzenbiomasse von Winterweizen auf dem schluffigen Boden höher waren als auf dem steinigen. Für den abgedeckten Bereich in der steinigen Anlage prognostizieren die Modelle F, FJ und C die Bodenfeuchte gleich gut und die Modell-optimierten Parameter waren vergleichbar. Die Parameter für die WWA des FJ Models und die wurzelhydrologischen Parameter für den Winterweizen waren übereinstimmend mit Literaturdaten. Mit den Modellen FJ und C konnten vergleichbare Stressfunktionen auf Skala des Wurzelsystems simuliert werden. Die Wurzelsystem-abhängigen Parameter des C Modells wurden belegt, die von FJ nicht. Wenn Modellparametrisierung und Simulationen auf alle Böden und Bewässerungstechniken ausgeweitet wurden, konnten die bodenhydrologischen Parameter gut mit dem FJ und dem C Modell identifiziert werden. Die Muster in der Pflanzen- und Wurzelentwicklung unterschieden sich zwischen den Plots beider Böden, was zu unterschiedlichen WWA Raten bedingt durch verschiedene Bodenwasserverfügbarkeiten führte. Das FJ und das C Modell simulierten ähnliche WWA Raten, welche am niedrigsten für den bedachten Plot im steinigen Boden war, wo die WWA niedriger war als die potentielle WWA. In dem schluffigen Boden waren die WWA Raten gleich der potentiellen WWA in allen drei Plots mit unterschiedlicher Bewässerungstechnik. Das C Modell prognostizierte die Transpirationsflussraten für beide Böden besser als das FJ Modell. Die Variationen der simulierten WWA zwischen den unterschiedlichen Plots stimmten mit den Xylemflussmessungen überein, jedoch benötigt der konstante Zeitabstand zwischen simulierten WWA Raten und Xylemfluss weitere Untersuchungen

Time-lapse geophysical assessment of agricultural practices on soil moisture dynamics

Geophysical surveys are now commonly used in agriculture for mapping applications. High-throughput collection of geophysical properties such as electrical conductivity (inverse of resistivity), can be used as a proxy for soil properties of interest (e.g. moisture, texture, salinity). Most applications only rely on a single geophysical survey at a given time. However, time-lapse geophysical surveys have greater capabilities to characterize the dynamics of the system, which is the focus of this work. Assessing the impact of agricultural practices through the growth season can reveal important information for the crop production. In this work, we demonstrate the use of time-lapse electrical resistivity tomography (ERT) and electromagnetic induction (EMI) surveys through a series of three case studies illustrating common agricultural practices (cover crops, compaction with irrigation, tillage with nitrogen fertilization). In the first case study, time-lapse EMI reveals the initial effect of cover crops on soil drying and the absence of effect on the subsequent main crop. In the second case study, compaction, leading to a shallower drying depth for potatoes was imaged by time-lapse ERT. In the third case study, larger change in electrical conductivity over time were observed in conventional tillage compared to direct drill using time-lapse EMI. In addition, different nitrogen application rates had significant effect on the yield and leaf area index but only ephemeral effects on the dynamics of electrical conductivity mainly after the first application. Overall, time-lapse geophysical surveys show great potential for monitoring the impact of different agricultural practices that can influence crop yield

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.The two-layer model of Shuttlerworth and Wallace (SW) was evaluated to estimate actual evapotranspiration (ETa) above a drip-irrigated Merlot vineyard, located in the Talca Valley, Region del Maule, Chile (35° 25' LS; 71° 32' LW ; 136m above the sea level). An automatic weather system was installed in the center of the vineyard to measure climatic variables (air temperature, relative humidity, and wind speed) and energy balance components (solar radiation, net radiation, latent heat flux, sensible heat flux, and soil heat flux) during November and December 2006. Values of ETa estimated by the SW model were tested with latent heat flux measurements obtained from an eddy-covariance system on a 30 minute time interval. Results indicated that SW model was able to predict ETa with a root mean square error (RMSE) of 0.44 mm d-1 and mean absolute error (MAE) of 0.36 mm d-1. Furthermore, SW model predicted latent heat flux with RMSE and MAE of 32 W m-2 and 19W m-1, respectively

USCID Fourth international conference on irrigation and drainage

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.Integrated regional water management -- Change of irrigation water quantity according to farm mechanization and land consolidation in Korea -- Local stakeholders participation for small scale water resources management in Bangladesh -- Water user participation in Egypt -- The man swimming against the stream knows the strength of it -- Roles and issues of Water Users' Associations for Sustainable Irrigation and Drainage in the Kyrgyz Republic and Uzbekistan in Central Asia -- Chartered Water User Associations of Afghanistan -- Updated procedures for calculating state-wide consumptive use in Idaho -- Measuring and estimating open water evaporation in Elephant Butte Reservoir in New Mexico -- Evapotranspiration of deficit irrigated sorghum and winter wheat -- Evaluation of a two-layer model to estimate actual evapotranspiration for vineyards -- Estimating pecan water use through remote sensing in Lower Rio Grande -- Estimating crop water use from remotely sensed NDVI, crop models, and reference ET -- Alfalfa production using saline drainage water -- Performance evaluation of subsurface drainage system under unsteady state flow conditions in coastal saline soils of Andhrapradesh, India -- Management strategies for the reuse of wastewater in Jordan -- Providing recycled water for crop irrigation and other uses in Gilroy, California -- Oakdale Irrigation District Water Resources Plan -- Use of information technology to support integrated water resources management implementation -- Decision-support systems for efficient irrigation in the Middle Rio Grande -- Salt management -- Ghazi Barotha Project on Indus River in Pakistan -- Field tests of OSIRI -- Water requirements, irrigation evaluation and efficiency in Tenerife's crops (Canary Islands, Spain) -- Using wireless technology to reduce water use in rice production -- Variability of crop coefficients in space and time -- Assessing the implementation of integrated water management approach in closed basins -- New strategies of donors in the irrigation sector of Africa -- Holistic perspective for investments in agricultural drainage in Egypt -- Mapping system and services for canal operation techniques -- An open channel network modernization with automated structures -- Canal control alternatives in the irrigation district 'Sector BXII del Bajo Guadalquivir,' Spain -- Hydrodynamic behavior of a canal network under simultaneous supply and demand based operations -- Simulation on the effect of microtopography spatial variability on basin irrigation performance -- Drip irrigation as a sustainable practice under saline shallow ground water conditions -- Water retention, compaction and bean yield in different soil managements under a center pivot system -- Precision mechanical move irrigation for smallholding farmers -- Wild flood to graded border irrigation for water and energy conservation in the Klamath basin -- A method describing precise water application intensity under a CPIS from a limited number of measurements -- An irrigation sustainability assessment framework for reporting across the environmental-economic-social spectrum -- Planning for future irrigation landscapes -- One size does not fit all -- Water information networks -- Improving water use efficiency -- Irrigation system modernization in the Middle Rio Grande Valley -- Relationship of operation stability and automatic operation control methods of open canal -- Responsive strategies of agricultural water sector in Taiwan -- Effect of network water distribution schedule and different on-farm water management practices on sugarbeet water use efficiency -- Variable Frequency Drive (VFD) considerations for irrigation -- Accuracy of radar water level measurements -- Transition submergence and hysteresis effects in three-foot Cutthroat flumes -- Practical irrigation flow measurement and control -- Linear anionic PAM as a canal water seepage reducing technology -- In-situ non-destructive monitoring of water flow in damaged agricultural pipeline by AE -- Reoptimizing global irrigation systems to restore floodplain ecosystems and human livelihoods -- Water management technologies for sustainable agriculture in Kenya -- Impacts of changing rice irrigation practices on the shallow aquifer of Nasunogahara basin, Japan -- Drought protection from an in-lieu groundwater banking program -- Development of agricultural drought evaluation system in Korea -- Bean yield and root development in different soil managements under a center pivot system -- Can frost damage impact water demand for crop production in the future? -- Real time water delivery management and planning in irrigation and drainage networks -- Growth response of palm trees to the frequency of irrigation by bubblers in Khuzestan, Iran -- Application of Backpropagation Neural Network to estimate evapotranspiration for ChiaNan irrigated area, Taiwan -- Increasing water and fertilizer use efficiency through rain gun sprinkler irrigation in sugar cane agriculture

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.A In order to promote irrigation sustainability through reporting by irrigation water managers around Australia, we have developed an adaptive framework and methodology for improved triple-bottom-line reporting. The Irrigation Sustainability Assessment Framework (ISAF) was developed to provide a comprehensive framework for irrigation sustainability assessment and integrated triple-bottom-line reporting, and is structured to promote voluntary application of this framework across the irrigation industry, with monitoring, assessment and feedback into future planning, in a continual learning process. Used in this manner the framework serves not only as a "reporting tool", but also as a "planning tool" for introducing innovative technology and as a "processes implementation tool" for enhanced adoption of new scientific research findings across the irrigation industry. The ISAF was applied in case studies to selected rural irrigation sector organisations, with modifications to meet their specific interests and future planning

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Salt management is a critical component of irrigated agriculture in arid regions. Successful crop production cannot be sustained without maintaining an acceptable level of salinity in the root zone. This requires drainage and a location to dispose drainage water, particularly, the salts it contains, which degrade the quality of receiving water bodies. Despite the need to generate drainage water to sustain productivity, many irrigation schemes have been designed and constructed with insufficient attention to drainage, to appropriate re-use or disposal of saline drainage water, and to salt disposal in general. To control the negative effects of drainage water disposal, state and federal agencies in several countries now are placing regulations on the discharge of saline drainage water into rivers. As a result, many farmers have implemented irrigation and crop management practices that reduce drainage volumes. Farmers and technical specialists also are examining water treatment schemes to remove salt or dispose of saline drainage water in evaporation basins or in underlying groundwater. We propose that the responsibility for salt management be combined with the irrigation rights of farmers. This approach will focus farmers' attention on salt management and motivate water delivery agencies and farmers to seek efficient methods for reducing the amount of salt needing disposal and to determine methods of disposing salt in ways that are environmentally acceptable

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.Since 3000 BC, rice has been the main crop in the Korean Peninsula, and where currently most of the available irrigation water is used to grow paddy rice. Methods for calculating the quantity of irrigation water required developed in the 1990's were compared to quantities measured in the field. The largest difference between calculated and measured quantities occurred in April and May. Based on field data we obtained in the middle part of the Korean Peninsula, significant changes have occurred in rice management, which has changed the amount of irrigation water required. Rice is now transplanted earlier, and duration of the transplanting phase on the regional scale is shorter through mechanization and consolidation of land holdings. These changes need to be taken into account when calculating the quantity of water needed for irrigation

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.Experiences establishing Water User Associations (WUAs) in Egypt have been carried out for the past 15 years, with increasingly promising results. Most of these activities have been pilot projects aiming to demonstrate the benefits and sustainability of WUAs. They were consequently implemented through a centralized and resource-intensive process and focused on limited numbers of associations. Since 2003, the Ministry of Water Resources and Irrigation (MWRI) has adopted as policy the large-scale development of Branch Canal WUAs. With support from USAID, about 600 branch canal WUAs (BCWUAs) have since been established, covering 15% of Egypt's irrigated area and involving half a million farmers and residents. In order to achieve this impressive outcome, a different approach has been developed and implemented, emphasizing the direct involvement of MWRI field staff and a partnership between water users and MWRI managers. This paper also argues that the conventional approach of forming WUAs by focusing on water users, and empowering them to take over the O&M responsibilities of irrigation systems, is not adapted to the Egyptian context