Estimation of natural ground water recharge for the performance assessment of a low-level waste disposal facility at the Hanford Site

In 1994, the Pacific Northwest Laboratory (PNL) initiated the Recharge Task, under the PNL Vitrification Technology Development (PVTD) project, to assist Westinghouse Hanford Company (WHC) in designing and assessing the performance of a low-level waste (LLW) disposal facility for the US Department of Energy (DOE). The Recharge Task was established to address the issue of ground water recharge in and around the LLW facility and throughout the Hanford Site as it affects the unconfined aquifer under the facility. The objectives of this report are to summarize the current knowledge of natural ground water recharge at the Hanford Site and to outline the work that must be completed in order to provide defensible estimates of recharge for use in the performance assessment of this LLW disposal facility. Recharge studies at the Hanford Site indicate that recharge rates are highly variable, ranging from nearly zero to greater than 100 mm/yr depending on precipitation, vegetative cover, and soil types. Coarse-textured soils without plants yielded the greatest recharge. Finer-textured soils, with or without plants, yielded the least. Lysimeters provided accurate, short-term measurements of recharge as well as water-balance data for the soil-atmosphere interface and root zone. Tracers provided estimates of longer-term average recharge rates in undisturbed settings. Numerical models demonstrated the sensitivity of recharge rates to different processes and forecast recharge rates for different conditions. All of these tools (lysimetry, tracers, and numerical models) are considered vital to the development of defensible estimates of natural ground water recharge rates for the performance assessment of a LLW disposal facility at the Hanford Site

Evapotranspiration in a subarctic agroecosystem: field measurements, modeling and sustainability perspectives

Thesis (Ph.D.) University of Alaska Fairbanks, 2015Northern latitudes are known to be the most vulnerable regions already witnessing the impacts of climate change. These impacts have not only affected a broad spectrum of ecological conditions but also physical and socio-economic functions and activities across the region. Uncertainties in climate change and its progression exposes agroecosystem development and sustainability to a great risk. Yet, not fully understood, climate feedbacks and influencing factors such as human population growth and consumption imposes economical and financial stress in the sustainability of agroecosystem activities. On the opposite direction, trends in this activity can drive regional modifications to climate to an extent that is still unknown and not yet forecasted. Over time, as the acreages of agricultural lands increase from conversion of natural lands such as boreal forests, unexpected changes in surface energetics and particularly overturning of evapotranspiration rates and changes in soil moisture regime may potentially accentuate regional climate change. These changes therefore are expected to introduce new challenges for Alaskan agriculturists because of increasing vulnerabilities and affecting conditions that shape resilience of agricultural systems and production. This research focused on improving understanding of surface energetics in an agroecosystem of Interior Alaska. A synthesis study was conducted combining the analysis of intensive field experiments including direct measurements of micrometeorological, hydrological, meteorological variables and computational modelling during the summer growing season. The evaluation of evapotranspiration (ET) dynamical regime and surface energy processes showed that ET represented a large portion of surface energy balance with similar aspects to surface fluxing levels in Arctic tundra, and in contrast, with more abundant flux levels than in subarctic boreal forest. Surface heterogeneities due to soil moisture and temperature regime drive differences in energy balance closure as a function of spatial scales despite the mostly flat surfaces and stationary atmospheric surface layer flows in the experimental area. A fully coupled numerical simulation was performed to model fluxes at the land-atmosphere interface and compared to independent observations of surface energy. A final assessment of experimental methodologies and numerical modeling is presented in preparation for integrative data fusion analysis and studies involving new satellite remote sensing capabilities, physical modeling and network field observations

Measuring and modelling soil evaporation in an irrigated olive orchard to improve water management

The aim of this study was to estimate soil evaporation (Es) in an intensive olive orchard. Measurements of Es were performed for 19 days using microlysimeters, during summers 2010, 2011 and 2012 in southeast Portugal. In order to relate each area type to radiation transmissivity, ground cover measurements were performed over the years. These data were used to calibrate and validate an empirical model for Es estimation. Measured daily average Es was 0.55 0.14 mm; the model estimated 0.53 0.18 mm for the same days, with a determination coe cient of 0.94. This corresponds to 9% of the reference evapotranspiration, representing well the overall values estimated for the summer, except for days after rain. Regarding the wet area, measured Es for the validation data set was 2.42 L/(m2 of wet area), the estimated was 2.49 L/(m2 of wet area). Measured average Es in dry area (validation data set) was 0.42 L/(m2 of dry area), estimated Es was 0.43 L/(m2 of dry area). The large exposed dry area had a significant contribution to evaporation. On average, estimated Es during a typical Mediterranean summer was 10% of reference evapotranspiration, representing 30% of transpiration and 23% of evapotranspirationinfo:eu-repo/semantics/publishedVersio

Standard single and basal crop coefficients for field crops. Updates and advances to the FAO56 crop water requirements method

ReviewThis study reviews the abundant research on FAO56 crop coefficients, published following introduction of the FAO56 paper in 1998. The primary goal was to evaluate, update, and consolidate the mid-season and end-season single (Kc) and basal (Kcb) crop coefficients, tabulated for many field crops in FAO56. The review found that the prevalent approach for estimating crop evapotranspiration (ETc) is the FAO56 Kc-ETo approach, i.e., the product of the Kc and reference evapotranspiration (ETo). The FAO56 Kc-ETo approach requires use of the FAO56 PM-ETo grass reference equation with appropriate crop-specific Kc and/or Kcb. Reviewed research provided various approaches to determine Kc and Kcb and used a variety of actual crop ET (ETc act) measurements. Significant attention was placed on accessing the accuracy of the field measurements and models used in these studies. Accuracy requirements, upper limits for Kc values, and related causal errors are discussed. Conceptual approaches relative to Kc transferability requirements are provided with focus on standard crop conditions and use of the FAO56 segmented Kc curve. Papers selected to update Kc∕Kcb used the FAO56 PM-ETo, provided accurate measurements to determine and partition ETc act, and satisfied transferability requirements. Selected observed Kc and Kcb values were converted to standard, sub-humid climate as adopted in FAO56. Observed values, with respect to tabulated FAO56 Kc and Kcb, were used in consolidating updated values for crops within general categories of grain legumes, fiber crops, oil crops, sugar crops, small grain cereals, maize and sorghum, and rice. Ancillary data, e.g., maximum root depth and crop height, were also collected from selected literature and tabulated. Results showed good agreement between updated and original tabulated FAO56 Kc and Kcb, confirming the reliability of the FAO56 values. This indicates change in the Kc (ETc/ETo ratio) of crops has not occurred due to climate change during the past ≈sixty years. New Kc∕Kcb data for crops, not included in FAO56, are also now presented for several oil crops and pseudocereals. The approach adopted for rice differs from FAO56 because consideration was given to the numerous rice water management practices currently used and, thus, Kc∕Kcb values for the initial season of rice were also presented. The review also observed that many research papers did not satisfy the adopted requirements in terms of ETo method and/or the accuracy of ETc act determinations and, therefore, could not be used. Thus, emphasis is placed on adopting improved accuracy and quality control in future research aimed at determining Kc data comparable to presented values. The transferability of standard Kc and Kcb has been assured for the values tabulated herein. Improved future applications of the FAO56 Kc-ETo method should consider remote sensing observations when available, particularly in defining crop growth stages at given locationsinfo:eu-repo/semantics/publishedVersio

Evapotranspiration in a catchment dominated by eucalypt forest and woodland

There is on-going need for reliable estimates of evapotranspiration (ET) at catchment scales to support objective decision-making for managing water supplies, and enhancing understanding of processes and modelling. Without reliable estimates of ET, water supply and catchment management agencies are exposed to significant economic, social and even environmental risks. This thesis focuses on identifying possible methodologies for estimating ET in a catchment dominated by eucalypt forest and woodland. More specifically, this thesis tests the hypothesis that different methods of deriving daily, catchment ET for a headwater in Australia meet underlying assumptions and yield similar results. The hypothesis was tested by using three approaches to estimate catchment ET: soil moisture changes (point scale), satellite imagery of leaf area index (MODIS, hillslope scale), and discharge (streamflow) and the storage-discharge relationship (catchment scale). Data from Corin Catchment, an unregulated catchment vital to the Australian Capital Territory and the surrounding region, is the basis of this study. After the General Introduction (Chapter 1), methods for estimating ET in eucalypt communities throughout Australia at various temporal and spatial scales are systematically reviewed (Chapter 2). Of the 1614 original research papers investigated, 52 were included for further investigation. A clear outcome is that transpiration by the overstorey, measured using sap flow, is the most frequently measured component of ET, and that physiological studies dominate estimates of ET. Very few studies were conducted at the catchment scale. Further, scaling ET from tree to catchment scales was rarely attempted, and the effect of scaling for water resource management is mostly unquantified and requires attention. The first method used to calculate catchment ET is based on up-scaling of soil moisture changes on the basis of a digital soil map (Chapter 4). The data presented here rejects the hypothesis that ET (derived from soil moisture) and overstorey transpiration (derived from sap flow) are well correlated. Instead, the data suggest that soil moisture-derived ET and overstorey transpiration obtained water from different sources. The key findings of this chapter are that this approach is not suitable for estimating ET at catchment scales because it is restricted to drier periods, and because trees did not solely rely on the defined root-zone for water supply. The second method to calculate catchment scale ET (Chapter 5) tests if hillslope-scale satellite imagery (MODIS leaf area index) can be up-scaled to estimate catchment ET. An outcome of this work is that caution is needed when using MODIS leaf area index for water resource planning in evergreen forests across the globe, particularly for forests with significant understorey and a relatively open overstorey canopy at some periods of the year. This method is deemed not suitable for estimating ET over the study area. The third method to calculate catchment scale ET (Chapter 6) is based on integrating discharge using a single non-linear equation to characterise the study area. This method yielded catchment ET far greater (18 times larger) than the largest observed measure of potential ET. As with the method based on soil moisture changes, it was restricted to drier periods. This method was clearly unsuitable for estimating ET over the study area due to relatively quick recession, large range in hourly discharge and significant scattered recession at low discharge. Overall, this thesis rejects the hypothesis that different methods of deriving daily, catchment ET for a headwater in Australia meet underlying assumptions and yield similar results. An important limitation identified through this research is the ability to determine a ‘correct’ estimate of catchment ET. Further research should focus on enhancing understanding of scaling ET within and beyond Australia, generating more daily catchment ET from up-scaled soil moisture changes, further evaluating ET from up-scaled satellite imagery, and identifying catchment characteristics to allow ET to be derived from discharge. Water resource managers must be diligent when selecting and applying a method to estimate catchment ET

Quantifying the water use and water productivity of apple orchards under fixed and draped nets

Thesis (PhDAgric)--Stellenbosch University, 2024.ENGLISH ABSTRACT: Apple (Malus domestica Borkh.) producers are increasingly using protective nets to address climate and fruit related challenges. There is insufficient quantitative information on the potential co-benefits of irrigation water savings in orchards under nets. This study firstly assessed the effects of two types of protective nets on microclimate variables. Secondly, the study aimed to establish if there are significant water savings and improvements in crop water productivity by using this technology. Lastly, the study investigated the effects of protective nets on apple tree physiology and water relations. White fixed net in the Koue Bokkeveld region (KBV) reduced daily total solar radiation by on average ~ 12%, wind speed by ~ 36%, and reference evapotranspiration by ~ 12%. Seasonal transpiration (T) was 11% lower under the net, while evapotranspiration (ET) was only 4% lower. The net reduced irrigation water requirement by about 4%. Peak mid-season basal crop coefficients (Kcb) were 0.54±0.02 and 0.59±0.02 with no differences in the single crop coefficients (Kc = 1.07±0.04 and 1.13±0.06) for the nets and control treatments, respectively. Transpiration based crop water productivity (WP) below the net was 20.7 kg m-3 compared to 18.2 kg m-3 in the open, with no differences in the ET-based WP values between the open and netted orchards. Black draped net tested in separate seasons in the KBV and Villiersdorp production regions reduced the daily total solar radiation by ~ 36% and ~ 31%, respectively. Wind speed was reduced by ~ 33% (KBV) and ~ 17% (Villiersdorp). Seasonal T was 8.5% and 8.3% lower under the net compared to the open in the two respective regions. Seasonal ET under the net declined by 7% in KBV and increased by 16% in Villiersdorp. Peak mid-season basal crop coefficients (Kcb) were 0.45±0.04 and 0.50±0.04 at KBV, and 0.74±0.18 and 0.77±0.19 at Villiersdorp for the draped net and control treatments, respectively. Transpiration-based crop water productivity (WP) was 25.5 kg m-3 under the net and 23.2 kg m-3 in the open at KBV, and 16.8 and 12.6 kg m-3 respectively, at Villiersdorp. The ET-based WP values were 19.3 and 14.8 kg m-3 for the net and control treatments, respectively, at KBV. At Villiersdorp, the values were 14.1 and 14.3 kg m-3 for the net and control treatments. Irrigation water productivity increased by 15% and 10.5% in the draped netted orchards in the two regions. Both pre-dawn and midday leaf water potential under the two net types were increased compared to the open. Net CO2 assimilation rate, transpiration rate and stomatal conductance were lower under the net, and the instantaneous leaf water use efficiency (WUEinst) was increased by the nets. Overall, the findings of the study show that the actual water saving benefits provided by fixed nets are smaller than expected possibly due to increased ET relating to a more active ground cover. However, a more substantial water saving benefit is possible in netted apple orchards if ET can be optimized through adapted management practices.AFRIKAANSE OPSOMMING: Appel (Malus domestica Borkh.) produsente gebruik toenemend beskermende nette om klimaat- en vrugteverwante uitdagings aan te spreek. Daar is onvoldoende kwantitatiewe inligting oor die potensiële byvoordele van besproeiingswaterbesparing in boorde onder nette. Hierdie studie het eerstens die uitwerking van twee tipes beskermende nette op mikroklimaatveranderlikes beoordeel. Tweedens was die studie daarop gemik om vas te stel of daar beduidende waterbesparings en verbeterings in gewaswaterproduktiwiteit is deur hierdie tegnologie te gebruik. Laastens het die studie die uitwerking van beskermende nette op appelboomfisiologie en waterverhoudings ondersoek. Wit vaste net in die Koue Bokkeveld-streek (KBV) het daaglikse totale sonbestraling met gemiddeld ~ 12% verminder, windspoed met ~ 36%, en verwysingsevapotranspirasie met ~ 12%. Seisoenale transpirasie (T) was 11% laer onder die net, terwyl evapotranspirasie (ET) slegs 4% laer was. Die net het besproeiingswaterbehoefte met sowat 4% verminder. Piek mid-seisoen basale gewaskoëffisiënte (Kcb) was 0.54±0.02 en 0.59±0.02 met geen verskille in die enkel gewaskoëffisiënte (Kc = 1.07±0.04 en 1.13±0.06) vir die nette en kontrole behandelings, onderskeidelik. Transpirasie gebaseerde gewaswaterproduktiwiteit (WP) onder die net was 20.7 kg m⁻³ vergeleke met 18.2 kg m⁻³ sonder net, met geen verskille in die ET-gebaseerde WP-waardes tussen die oop en bedekte boorde nie. Swart gedrapeerde net wat in afsonderlike seisoene in die KBV- en Villiersdorp- produksiestreke getoets is, het die daaglikse totale sonbestraling met onderskeidelik ~36% en ~31% verminder. Windspoed is verminder met ~ 33% (KBV) en ~ 17% (Villiersdorp). Seisoenale T was 8.5% en 8.3% laer onder die netto in vergelyking met die oop in die twee onderskeie streke. Seisoenale ET onder die net het met 7% in KBV gedaal en in Villiersdorp met 16% toegeneem. Piek mid-seisoen basale gewaskoëffisiënte (Kcb) was 0.45±0.04 en 0.50±0.04 in KBV, en 0.74±0.18 en 0.77±0.19 in Villiersdorp vir die gedrapeerde net en kontrole behandelings, onderskeidelik. Transpirasie-gebaseerde gewaswaterproduktiwiteit (WP) was 25.5 kg m⁻³ onder die net en 23.2 kg m⁻³ sonder net in KBV, en 16.8 en 12.6 kg m⁻³ onderskeidelik, in Villiersdorp. Die ET-gebaseerde WP waardes was 19.3 en 14.8 kg m⁻³ vir die net en kontrole behandelings, onderskeidelik, in KBV. In Villiersdorp was die waardes 14.1 en 14.3 kg m⁻³ vir die net- en kontrolebehandelings. Besproeiingswaterproduktiwiteit het met 15% en 10.5% in die gedrapeerde net boorde in die twee streke toegeneem. Beide voor sonsopkoms - en mid-dag blaarwaterpotensiaal is verhoog onder die twee nettipes in vergelyking met geen net. Netto CO2 assimilasietempo, transpirasietempo en stomatale geleiding was laer onder die net, en die oombliklike blaarwatergebruiksdoeltreffendheid (WUEinst) is deur die nette verhoog. Oor die algemeen toon die bevindinge van die studie dat die werklike waterbesparingsvoordele wat deur vaste nette verskaf word, kleiner is as wat verwag is, moontlik as gevolg van verhoogde ET wat verband hou met 'n meer aktiewe grondbedekking. 'n Meer aansienlike waterbesparingsvoordeel is egter moontlik in netbedekte appelboorde as ET geoptimaliseer kan word deur aangepaste bestuurspraktyke.Doctora

Watershed Management on Range and Forest Lands Proceedings of the Fifth Workshop of the United States/Australia Rangelands Panel

Preface: The U.S.-Australia Cooperative Rangeland Science Program In October 1968 the governments of the United States and Australia entered into an agreement for the purpose of facilitating close cooperative activities between the scientific communities of the two countries. The joint communique issued at that time designated the U.S. National Science Foundation and the Australian Commonwealth Department of Education and Science as the coordinating agencies. Both countries were to encourage binational teamwork in research, interchanges of scientists, joint seminars, and exchanges of information. A United States-Australia Rangeland Panel was established in December 1969 to further cooperation between the two countries in the rangeland sciences. The present panel includes the following

Factors affecting dewfall, its measurement with lysimeters, and its estimation with micrometerological equations

Aus der Energiebilanzgleichung wurden Lufttemperatur, Bewölkung, Windgeschwindigkeit, Bodenwärmestrom und relative Luftfeuchte als die meteorologischen Faktoren ermittelt, die Taubildung bestimmen. Alle fünf sind gleich wichtig. Durch Platzieren von verschiedenen Gewichten ergab sich bei niedrigen Windgeschwindig-keiten (u) eine Wiegegenauigkeit der Lysimeter hier (Gesamtmasse ~3700 kg) von 20 g. Das genügt für Taustudien. Mit steigendem u nimmt sie ab. Lysimeterdaten zeigten weniger Tau auf brachem Boden als auf Dauer-Gras. Nach dem Pflanzen von Feldfrüchten stieg die Taumenge mit dem Wachstum an und übertraf bald die Menge auf Gras. Nach der Ernte fiel sie wieder unter die Graswerte. Mit der Bowen ratio oder Penman-Monteith Gleichung berechnete Taumengen folgten dem gleichen Trend wie per Lysimeter gemessene. Beide Berechnungswege stimmten überein, aber die berechneten Werte waren höher und konstanter. Ungenaue Bodenwärmestromda-ten waren der vermutliche Grund für die Abweichungen.von Huijie Xia