As the main component of terrestrial energy and water balance, evapotranspiration (ET) moves a large amount of water and energy in the form of latent heat flux from bare soil and vegetated surfaces into the atmosphere. Despite the development of many methods and equations through past decades, accurate ET estimation is still a challenging task, especially for the Red River Valley of the North (RRV) that has limited updated information on ET either for landscape or agricultural water management. The overall objective of first study was to evaluate the ASCE-EWRI reference ET (ETo) method by developing an accurate crop coefficient (Kc) using an eddy covariance (EC) system over an unirrigated turfgrass site. The results showed that with mean ETgrass/ETo ratio as 0.96 for the entire growing seasons of turfgrass, the ASCE-EWRI ETo method is valid for guiding the turfgrass irrigation management in cold climate conditions. In a Controlled drainage with subirrigation (CD+SI) field, an EC system was used to measure and quantify energy flux components along with soil water content (SWC) and water table depth (WTD) measurements during four corn growing. This study showed that the subsurface drainage along with the CD + SI system can be used for optimal water management with an improvement of 26.7% and 6.6% of corn yield during wet and dry year, respectively. For the final task, ET was measured using EC, Bowen ratio system (BREB), and soil water balance (SWB) method during the corn growing season. The comparison of the EC and the BREB system illustrated the advantages of using the residual method to close the energy balance closure of EC. Among the different time approaches for SWB method, ET by the SWB method using the average soil water contents between 24:00 to 2:00 time period showed non-significant differences (alpha = 0.05) compared to the BREB system during the observation periods. / USDA National Institute of Food and Agriculture project / USDA NCR SARE project / ND Soybean Council / ND Water Resources Research Institute / ND Agricultural Experimental Station / USDA Hatch project / NASA ROSES Project

To close the water use budget of irrigated agricultural fields in floodplains with substantial riparian corridors, it is necessary to understand groundwater usage by dominant phreatophytic vegetation, particularly when the primary source of water for irrigation comes from groundwater abstraction. We report here results of estimated evapotranspiration (ET) of a riparian forest, which were based on measurements of sap flow in phreatophytic vegetation within a riparian corridor. The riparian corridor was within a study area 75 to 140 meters wide in the lower portion of the Scotts Creek watershed, which is bounded to the west by the Pacific Ocean in Santa Cruz County, California. Canopy coverage in the study area often approaches 100% during the growing season, with dominant trees being red alder (Alnus rubra Bong.), arroyo willow (Salix lasiolepis Benth.), and pacific willow (Salix lasiandra Benth. var. lasiandra). Other trees include boxelder (Acer negundo L.), bigleaf maple (Acer macrophyllum Pursh.), California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.), and coastal redwoods (Sequoia sempervirens (D. Don) Endl.). Common understory vegetation includes California blackberry (Rubus ursinus Cham. and Schlecht.), stinging nettle (Urtica dioica subsp. gracilis L.), poison hemlock (Conium maculatum L.), Cape ivy (Delairea odorata Lem.), Italian thistle (Carduus pycnocephalus L. subsp. pycnocephalus), and western poison oak (Toxicodendron diversilobum (Torr. & A. Gray) Greene). We hypothesized that the ET of a riparian forest could be estimated by measuring the sap flow of riparian phreatophytic trees. For the study reported here, only the two most dominant phreatophytic species, namely red alders and arroyo willows, were instrumented with thermal dissipation probes. In addition to diurnal fluctuations, sap flow data collected hitherto also showed expected seasonal variation with summer maxima and winter minima, with transition fall and spring periods. Sap flow measurements from the study area were used to estimate riparian forest ET by projecting them across the canopy areal extent of the riparian forest using sampled tree sapwood areas from six sample plots. The sap flow-based ET results were then compared to ET results reported by two other methods. Additional research, including increased number of trees with thermal dissipation probes, further analysis of sap flow behavior, and continued long-term measurement of sap flow, is needed to further improve the method of using long-term sap flow measurements to estimate the ET of a riparian forest.

No description available.

This study evaluated the potential of using the Surface Energy Balance Algorithm for Land (SEBAL) as a means for estimating evapotranspiration (ET) for local and regional scales in Southern Idaho. The original SEBAL model was refined during this study to provide better estimation of ET in agricultural areas and to make more reliable estimates of ET from other surfaces as well, including mountainous terrain. The modified version of SEBAL used in this study, termed as SEBALID (lD stands for Idaho) includes standardization of the two SEBAL "anchor" pixels, the use of a water balance model to track top soil moisture, adaptation of components of SEBAL for better prediction of the surface energy balance in mountains and sloping terrain, and use of the ratio between actual ET and alfalfa reference evapotranspiration (ETr) as a means for obtaining the temporal integration of instantaneous ET to daily and seasonal values. Validation of the SEBALID model at a local scale was performed by comparing lysimeter ET measurements from the USDA-ARS facility at Kimberly, Idaho, with ET predictions by SEBAL using Landsat 5 TM imagery. Comparison of measured and predicted ET values was challenging due to the resolution of the Landsat thermal band (120m x 120 m) and the relatively small size of the lysimeter fields. In the cases where thermal information was adequate, SEBALID predictions were close to the measured values of ET in the lysimeters. Application of SEBALID at a regional scale was performed using Landsat 7 ETM+ and Landsat 5 TM imagery for the Eastern Snake Plain Aquifer (ESP A) region in Idaho during 2000. The results indicated that SEBALID performed well for predicting daily and seasonal ET for agricultural areas. Some unreasonable results were obtained for desert and basalt areas, due to uncertainties of the prediction of surface parameters. In mountains, even though validation of results was not possible, the values of ET obtained reflected the progress produced by the refinements made to the original SEBAL algorithm.

Evapotranspiration has been defined as the combination of evaporation of water from the soil surface and transpiration of water by vegetation. If the ground is well covered by plants, most of the water is lost by transpiration of water directly from the plant tissue, rather than by evaporation of water directly from the soil surface. The term consumptive use is synonymous with evapotranspiration.

Water is undeniably among the most important natural resources and the most critical in semi-arid regions like the Intermountain West of the United States. Such regions are characterized by low precipitation, the majority of which is transferred to the atmosphere from the soil and vegetation as evapotranspiration (ET). Quantification of ET is thus crucial for understanding the balance of water within the region, which is important for efficiently planning the available water resources. This study was motivated towards advancing the estimation of actual ET (ETA) in mountain ecosystems, where the variation in different types of vegetation and non-uniformity of soil including considerable stone content creates challenges for estimating water use as ET. With the aim of addressing the effect of stone content in controlling soil moisture and ET, this study examined the influence of stone content on bulk soil hydraulic properties. An averaging model referred to as a binary mixing model was used to describe the way in which water is held and released in stony soil. This approach was based on the individual hydraulic behavior of the background soil and of the stones within the soil. The effect of soil stone content on ETA was evaluated by accounting for the water retention properties of stones in the soil using a numerical simulation model (HYDRUS-1D). The results revealed overestimation of simulated ETA when effects of stone content were not accounted for in comparison to ETA measured by the state-of-the-art “eddy covariance” measurement method for ETA. An even larger-scale model was evaluated, named the Noah-Multiphysics (Noah-MP) land surface model. The land surface model was run using different arrangements of complexity to determine the importance of stone content information on simulation results. The version of the model with information about stone content along with detailed soil properties was able to provide the best Noah-MP prediction of ET. The study suggests that improvement in representation of soil properties including stone content information, can substantially advance the ability of numerical and land surface models to more accurately simulate soil water flow and ETA.

Evapotranspiration (ET) of center pivot irrigated alfalfa was studied in the windy, arid, Curlew Valley, Northern Box Elder County, Utah, during the summers of 2009 and 2010. ET was estimated using eddy covariance (EC) and surface renewal (SR) techniques. ET estimates from the EC and SR analyses were compared with estimates using ASCE Standardized Reference ET Equation, with both dual and mean crop coefficients. EC energy balance closure was 0.80, on average, in 2009 and 0.76 in 2010. The SR weighting parameter (α) was calculated through linear regression of EC and SR sensible heat flux estimates. Alpha was found to be 0.70 if EC energy balance closure was forced and 0.55 if closure was not forced. ET from SR analysis with α = 0.70 (ETSRα=0.70) was 409 mm in 2009 and 331 mm in 2010. ET from EC analysis with forced closure (ETECforced) was 390 mm in 2009 and 326 mm in 2010. In contrast, ETSRα=0.55 was 408 and 333 mm in 2009 and 2010, respectively, while ETECunforced was 315 and 251 mm in 2009 and 2010, respectively. Combined ETECforced and ETSRforced were compared with estimated crop ET from the ASCE Std. Eq. with both dual and mean crop coefficients (ETcDual and ETcm, respectively). ETcDual was 689 mm in 2009, as compared to ETcm and ETEC-SRforced, which were 677 and 617 mm, respectively. In 2010 ETcDual was 674 mm, with ETcm and ETEC-SRforced being 629 and 576 mm, respectively. The Kcm approach more closely approximated the estimated wet soil evaporation determined from the ETEC-SRforced for the measurement conditions and stated assumptions. ETEC-SR estimates were compared with irrigation application information to approximate field scale water balances. Effective precipitation plus net irrigation application (less wind drift and evaporation) were nearly equal to ETEC-SRforced for 2nd and 3rd crops of alfalfa in 2009 and 2010. No deep percolation was calculated using ETEC-SRforced; however, soil moisture measurements were not sufficient to verify that this was true. The water balances suggested that the fields were being underirrigated which may have caused salt accumulation in the soil, as evidenced by the low reported yields.

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第13181号 / 論農博第2860号 / 新制||農||1061(附属図書館) / 学位論文||H30||N5103(農学部図書室) / (主査)教授 小杉 緑子, 教授 北山 兼弘, 教授 舟川 晋也 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

S-metolachlor is an effective herbicide used to control/suppress annual grasses, nutsedges and several broadleaf weeds in sweetpotato. However, a decline in storage root quality and yield has been reported under certain environmental conditions. Information is limited on the effect of S-metolachlor application followed immediately by rainfall on sweetpotato growth and development under different temperatures, as well as the optimum application time. Therefore, the objectives of this study were to evaluate sweetpotato responses to interactive effects of S-metolachlor, temperature and rainfall, and to determine S-metolachlor optimum application time. A sunlit, controlled environment experiment was conducted to investigate sweetpotato response to S-metolachlor and rainfall immediately after application under different temperatures. Sweetpotato slips were transplanted into sandy soil filled pots. Treatment combinations included five levels of S-metolachlor, 0.00, 0.86, 1.72, 2.58 and 3.44 kg ha-1, two levels of rainfall, 0 and 38 mm and three temperatures, 25/17, 30/22 and 35/27 °C, day/night. After POST application of S-metolachlor and rainfall, all plants were transferred to sunlit growth chambers that were maintained at their respective temperatures and ambient CO2 concentration for 60 days. In another experiment, S-metolachlor application time was varied to investigate sweetpotato growth and development. Two levels of S-metolachlor 0.0 and 1.0 kg ha-1 and three application times 0, 5 and 10 days after transplanting (DAT) were used and plants were harvested five times, 5, 10, 15, 20 and 80 DAT to estimate plant growth and development. Shoot, root and total plant biomass yields declined with increasing concentration of S-metolachlor across temperatures. In addition, storage root yield and quality decline was S-metolachlor rate dependent and aggravated by rainfall immediately after herbicide treatment across temperatures. S-metolachlor was more injurious on most plant component parameters in the optimum and high temperatures where plant growth was vigorous than in the low temperatures. S-metolachlor application at 0 and 5 days affected sweetpotato growth, including storage roots, but delaying until 10 days minimized the injury. These results can be used to weigh the risk of crop injury against the weed control benefits of S-metolachlor when making management decisions, and to determine application time based on weather information.

Hydroelectric releases on the Deerfield River in northwestern Massachusetts affect surface water-groundwater interactions there by daily reversing the head gradient between river and groundwater. Artificially elevated stage drives river water into the riparian aquifer. Water budget analysis indicates that roughly 10% of this bank-stored water is permanently lost from the river system in a 19.5 km reach, likely as a result of transpiration by bank vegetation. Field observations as well as two-dimensional modeling results show that water losses are not uniform throughout the study reach. Riparian aquifer transmissivity in river sub-reaches largely determines the magnitude of surface water-groundwater exchange as well as net water loss from the river. These newly documented dam-induced losses from river systems inform decisions by river managers and hydroelectric operators of additional tradeoffs of oscillatory dam-release river management.