Seasonal estimates of actual evapo-transpiration from Tamarix ramosissima stands using three-dimensional eddy covariance

This study addresses the pattern of evapo-transpiration (ET) throughout the growing season for Tamarix ramosissima between regularly flooded and unflooded sites. Spatial and temporal ET patterns along the Middle Rio Grande demonstrated considerable variability. ET at the unflooded site was 61% of ET at the flooded site, totaling 74 and 122 cm year-1 at the unflooded and flooded sites, respectively. The seasonal coefficient of variability was 37% and 38% at the flooded and unflooded sites, respectively. Spatial variability was 39%. Determining ET patterns with respect to the spatial, ecological and temporal setting improves riparian zone ET depletion predictions. © 2002 Elsevier Science Ltd

Is evapotranspiration more supplied by summer precipitation or winter precipitation: understanding precipitation sources of terrestrial water use and their variations across wetter and drier years and distinct eco-climatological regions

Abstract 1:The impacts of changing precipitation regimes on the contributions of different seasons’ precipitation to evapotranspiration (ET) versus runoff is not well known because empirical insights are scarce. However, such insights are important for improving model predictions of future water-resource availability and ecosystem responses to summer and winter droughts. Here we use using long-term measurements of fluxes and isotope ratios (δ18O) in runoff and precipitation to calculate the partitioning of seasonal precipitation between ET and runoff, using an end-member mixing and splitting framework and focusing on effects of wetter versus drier summers and winters. We hypothesized that drier summers would involve carryover of winter precipitation to mitigate shortages, but related findings were partially indeterminate. However, we did find increases in winter precipitation across a 500-mm range involved the fraction of ET from summer precipitation decreasing from 100% (within error) and the fraction of winter precipitation contributing to ET increasing from 0% (within error) to 21%. Although there were substantial uncertainties in the trends we identified, we expect that the novel approach used here could be a useful framework for understanding the sensitivity of ET partitioning to climatic change, especially where precipitation δ18O varies substantially between seasons.Abstract 2: To understand how changing patterns of seasonal precipitation inputs may affect ecosystems and water resources, we need to know how precipitation from different seasons travels through landscapes and contributes to runoff versus evapotranspiration (ET). In this study, we use stable isotope data measured in the National Ecology Observation Network (NEON) aquatic sites to quantify the partitioning of winter and summer precipitation into runoff and ET. Across the 23 watersheds, ranging in size from 1.1 to 47,000 km2, we found the fraction of summer precipitation routed to ET ranged from 0.13 to 1.00, which coincided with the fraction of ET composed of summer precipitation ranging from 0.04 to 0.76 (readers should note these ranges do not include implausible values generated for 4 sites where the available data were insufficient to constrain uncertainties). To identify factors that influence seasonal precipitation partitioning, a stepwise regression was used with a set of potential predictor variables related to topography, climate, and vegetation. Although many individual variables proved to be significant correlates, 83 % of the variation in the fraction of summer precipitation routed to ET was estimated by a 4-term model using chlorophyll carotenoid index (CCI) variability, mean annual precipitation, and enhanced vegetation indices (EVI) metrics. The fraction of ET sourced from summer precipitation was estimated by the ratio of summer precipitation to annual precipitation and minimum EVI. This is the first cross-site study on seasonal precipitation partitioning, and thus the findings here advance our fundamental understanding of how precipitation is routed to ET versus runoff in differing landscapes

A Compact Weighing Lysimeter to Estimate the Water Infiltration Rate in Agricultural Soils

Infiltration estimation is made by tests such as concentric cylinders, which are prone to errors, such as the lateral movement under the ring. Several possibilities have been developed over the last decades to compensate these errors, which are based on physical, electronic, and mathematical principles. In this research, two approaches are proposed to measure the water infiltration rate in a silty loam soil by means of the mass values of a lysimeter weighing under rainfall conditions and different moisture contents. Based on the fact that with the lysimeter it is possible to determine acting soil flows very precisely, then with the help of mass conservation and assuming a downward vertical movement, 12 rain events were analyzed. In addition, it was possible to monitor the behavior of soil moisture and to establish the content at field capacity from the values of the weighing lysimeter, from which both approach are based. The infiltration rate of these events showed a variable rate at the beginning of the rainfall until reaching a maximum, to descend to a stable or basic rate. This basic infiltration rate was 1.49 ± 0.36 mm/h, and this is because soils with fine textures have reported low infiltration capacity. Four empirical or semi-empirical models of infiltration were calibrated with the values obtained with our approaches, showing a better fit with the Horton’s model

Predictive Modeling of Organic Pollutant Leaching and Transport Behavior at the Lysimeter and Field Scales

Soil and groundwater pollution has become a global issue since the advent of industrialization and mechanized agriculture. Some contaminants such as PAHs may persist in the subsurface for decades and centuries. In a bid to address these issues, protection of groundwater must be based on the quantification of potential threats to pollution at the subsurface which is often inaccessible. Risk assessment of groundwater pollution may however be strongly supported by applying process-based simulation models, which turn out to be particularly helpful with regard to long-term predictions, which cannot be undertaken by experiments. Such reliable predictions, however, can only be achieved if the used modeling tool is known to be applicable. The aim of this work was threefold. First, a source strength function was developed to describe the leaching behavior of point source organic contaminants and thereby acting as a time-dependent upper boundary condition for transport models. For general application of these functions dimensionless numbers known as Damköhler numbers were used to characterize the reaction of the pollutants with the solid matrix. Two functions were derived and have been incorporated into an Excel worksheet to act as a practical aid in the quantification of leaching behavior of organic contaminant in seepage water prognoses. Second, the process based model tool SMART, which is well validated for laboratory scale data, was applied to lysimeter scale data from two research centres, FZJ (Jülich) and GSF (München) for long term predictions. Results from pure forward model runs show a fairly good correlation with the measured data. Finally, the derived source term functions in combination with the SMART model were used to assess groundwater vulnerability beneath a typical landfill at Kwabenya in Ghana. The predicted breakthrough time after leaking from the landfill was more than 200 years considering the operational time of the facility (30 years). Considering contaminant degradation, the landfill would therefore not cause groundwater pollution under the simulated scenarios and the SMART model can be used to establish waste acceptance criteria for organic contaminants in the landfill at KwabenyaSeit dem Beginn der Industrialisierung und der mechanisierten Landwirtschaft wurde die Boden- und Grundwasserverschmutzung zu einem weltweiten Problem. Einige Schadstoffe wie z. B. PAK können für Jahrzehnte oder Jahrhunderte im Untergrund bestehen. Um diese Probleme behandeln zu können, muss der Schutz des Grundwassers basierend auf der Quantifizierung potentieller Gefährdungen des zumeist unzugänglichen Untergrundes erfolgen. Risikoabschätzungen von Grundwasserverschmutzungen können jedoch durch die Anwendung prozess-basierter Simulationsmodelle erheblich unterstützt werden, die sich besonders im Hinblick auf Langzeitvorhersagen als hilfreich erweisen und nicht experimentell ermittelbar sind. Derart zuverlässige Vorhersagen können jedoch nur erhalten werden, wenn das verwendete Modellierwerkzeug als anwendbar bekannt ist. Das Ziel dieser Arbeit bestand aus drei Teilen. Erstens wurde eine Quellstärke-funktion entwickelt, die das Ausbreitungsverhalten organischer Schadstoffe aus einer Punktquelle beschreibt und dadurch als zeitabhängige obere Randbedingung bei Transportmodellen dienen kann. Im Hinblick auf die allgemeine Anwendbarkeit dieser Funktion werden als Damköhler-Zahlen bekannte, dimensionslose Zahlen verwendet, um die Reaktion von Schadstoffen mit Feststoffen zu charakterisieren. Zwei Funktionen wurden abgeleitet und in ein Excel-Arbeitsblatt eingefügt, das ein praktisches Hilfsmittel bei der Quantifizierung des Freisetzungsverhaltens organischer Schadstoffe im Rahmen der Sickerwasserprognose darstellt. Der zweite Teil dieser Arbeit beinhaltet die Anwendung des prozessbasierten und mittels Laborexperimenten validierten Modellwerkzeugs SMART für Langzeitprognosen auf der Lysimeterskala anhand von Daten zweier Forschungszentren, FZJ (Jülich) und GSF (München). Ergebnisse reiner Vorwärtsmodellierungsläufe zeigten gute Übereinstimmungen mit den gemessenen Daten. Im dritten Teil wurden die erhaltenen Quellstärkefunktionen in Kombination mit dem SMART-Modell eingesetzt, um das Grundwassergefährdungspotential unter einer typischen Deponie in Kwabenya, Ghana, einzuschätzen. Die vorhergesagten Durchbruchszeiten nach einer Leckage in der Deponie betragen über 200 Jahre bei einer Betriebszeit von 30 Jahren. Unter Berücksichtigung des Schadstoffabbaus verursacht die Deponie somit keine Grundwasserverunreinigung im Rahmen der simulierten Szenarien und das SMART-Modell kann verwendet werden, um Schadstoffgrenzwerte für organische Schadstoffe in der Deponie in Kwabenya festzulegen

USCID water management conference

Presented at Meeting irrigation demands in a water-challenged environment: SCADA and technology: tools to improve production: a USCID water management conference held on September 28 - October 1, 2010 in Fort Collins, Colorado.Includes bibliographical references.The Colorado Satellite-Linked Water Resources Monitoring System: 25 years later -- Using state water law for efficient water use in the West -- On-farm strategies for deficit or limited irrigation to maximize operational profit potential in Colorado's South Platte Basin -- Economics of groundwater management alternatives in the Republican Basin -- Effects of policies governing water reuse on agricultural crops -- Flow calibration of the Bryan Canal radial gate at the United Irrigation District -- Considering canal pool resonance in controller design -- Synthetic canal lining evaluation project -- South Platte Ditch Company: demonstration flow monitoring and data collection project -- The case for ditch-wide water rights analysis in Colorado -- Bore wells: a boon for tail end users -- Irrigation efficiency and water users' performance in water management: a case study on the Heran distributary, Sanghar, Sindh, Pakistan -- Initiating SCADA projects in irrigation districts -- Use of GIS as a real time decision support system for irrigation districts -- Interaction of Advanced Scientific Irrigation Management (ASIM) with I-SCADA system for efficient and sustainable production of fiber on 10,360 hectares -- Improving irrigation system performance in the Middle Rio Grande through scheduled water delivery -- Cost-effective SCADA development for irrigation districts: a Nebraska case study -- Accomplishments from a decade of SCADA implementation in Idaho's Payette Valley -- Critical success factors for large scale automation experiences from 10,000 gates -- Mapping ET in southeastern Colorado using a surface aerodynamic temperature model -- Alfalfa crop coefficients developed using a weighing lysimeter in southeast Colorado -- Turfgrass ET from small lysimeters in northeast Colorado -- Monitoring turf water status with infrared thermometry -- Training tool for on-farm water management using heuristic simulation software -- Water production functions for high plains crops -- Assessment of economic and hydrologic impacts of reduced surface water supply for irrigation via remote sensing -- Developing corn regional crop coefficients using a satellite-based energy balance model (ReSET) in the South Platte River area of Colorado

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

Doctor of Philosophy

dissertationAs one of the most important earth systems, the water cycle is significantly disrupted by changes to land cover and water management accompanying urbanization. Recently, researchers have developed a concept of near-natural hydrology to guide ecological engineering of urban systems to mitigate the impacts of development on the water cycle. Stormwater green infrastructure (GI) is one of the practices that has been used to restore the urban hydrology. The goal of this research is to answer the overarching question: Can GI implemented in a semiarid watershed restore the water budget to its predevelopment condition? Field experiments and hydrologic modeling were conducted in a semiarid city, Salt Lake City, Utah, U.S to answer this question. This work created, for the first time, an ET observation dataset for the semiarid intermountain west of the U.S. Based on the new dataset, empirical parameters for Penman-Monteith ET methods, including crop coefficients and surface resistances for green roofs, were identified and calibrated for this region, also for the first time. Their values can be directly used for ET modeling of green roofs in similar climates. An urban stormwater model, EPA SWMM, was modified to be able to represent spatially heterogeneous ET rates in one catchment for up to six types of land covers, including GI (bioretention, green roof), landscapes (turf, deciduous trees, coniferous trees), and water surface. This creates an improved platform to study the hydrologic response of urban watersheds by addressing the limitation of hydrologic models, not including GI and stormwater models with poor representation of ET. Also, the EPA SWMM was modified to be able to operate using subdaily ET time series input for the first time. With the updated model, the final part of this work studies the potential of restoring the predevelopment urban water budget by adopting GI strategies in a semiarid watershed. Based on the proposed water budget restoration coefficient, the water budgets have been restored due to GI applications 94%, 94%, and 82% of the predevelopment state in the dry, average, and wet years, respectively

How to integrate geochemistry at affordable costs into reactive transport for large-scale systems: Abstract Book

This international workshop entitled “How to integrate geochemistry at affordable costs into reac-tive transport for large-scale systems” was organized by the Institute of Resource Ecology of the Helmholtz-Zentrum Dresden Rossendorf in Feb-ruary 2020. A mechanistic understanding and building on that an appropriate modelling of geochemical processes is essential for reliably predicting contaminant transport in groundwater systems, but also in many other cases where migration of hazardous substances is expected and consequently has to be assessed and limited. In case of already present contaminations, such modelling may help to quantify the threads and to support the development and application of suitable remediation measures. Typical application areas are nuclear waste disposal, environmental remediation, mining and milling, carbon capture & storage, or geothermal energy production. Experts from these fields were brought together to discuss large-scale reactive transport modelling (RTM) because the scales covered by such pre-dictions may reach up to one million year and dozens of kilometers. Full-fledged incorporation of geochemical processes, e.g. sorption, precipitation, or redox reactions (to name just a few important basic processes) will thus create inacceptable long computing times. As an effective way to integrate geochemistry at affordable costs into RTM different geochemical concepts (e.g. multidimensional look-up tables, surrogate functions, machine learning, utilization of uncertainty and sensitivity analysis etc.) exist and were extensively discussed throughout the workshop. During the 3-day program of the workshop keynote and regular lectures from experts in the field, a poster session, and a radio lab tour had been offered. In total, 40 scientists from 28 re-search institutes and 8 countries participated

Ligand-Promoted Dissolution of Uranyl Phosphate Across Scales

The formation of uranyl phosphate precipitate is a remediation strategy because the low solubility of uranyl phosphate minerals, like chernikovite, limits the mobility of uranium in contaminated soils. However, organic ligands can complex with aqueous metal cations to form more soluble species. For example, citrate is a commonly occurring organic ligand produced by plants and microbes that increases the solubility of uranium and therefore the dissolution of uranyl phosphate minerals in the uranyl phosphate-citrate system. This effect is an important control on the mobility of uranium in organic-rich, and near-surface vegetated environments. Nevertheless, key aspects of the citrate-uranyl phosphate system remain poorly understood, and this limits the ability to assess risks of exposure and strategies for remediating uranium contaminated soils. The goals of this research are to determine the mechanism, extent, and rate of citrate-promoted dissolution of uranyl phosphate and evaluate how ligand-promoted dissolution and solid-phase transformations of uranyl phosphate affect macro-scale uranium transport. Batch dissolution, continuously stirred tank reactor (CSTR), soil column, and field lysimeter experiments were conducted to span across spatial scales ranging from Ångstrom to the meter scale. The results from all experiments indicate that the concentration of uranium dissolved from a chernikovite source increases with the concentration of citrate. However, this study determined that the rate of increase in uranium concentration diminishes at higher citrate concentrations and longer residence times and provided evidence of a uranyl-citrate alteration layer on the surfaces of uranyl phosphate grains after citrate exposure. These findings suggest that a combination of secondary-phase precipitation and ligand surface saturation hinder the release of uranium into solution. In the presence of soil, cations from the soil compete with uranium from the chernikovite to form citrate-complexes, slowing the dissolution of chernikovite. Soil cations, like potassium and calcium, can also integrate into the uranyl phosphate structure, altering the original chernikovite to a less soluble uranyl phosphate phase that is more resistant to citrate-promoted dissolution at lower citrate concentrations. The findings presented in this work show that although citrate promotes the dissolution of uranyl phosphate, other mechanisms hinder the release of uranium in the environment from a uranyl phosphate source