• An Advanced Risk Modeling Method to Estimate Legionellosis Risks Within a Diverse Population

      Weir, Mark H.; Mraz, Alexis L.; Mitchell, Jade; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth, Community Environm & Policy Dept (MDPI, 2019-12-20)
      Quantitative microbial risk assessment (QMRA) is a computational science leveraged to optimize infectious disease controls at both population and individual levels. Often, diverse populations will have different health risks based on a population's susceptibility or outcome severity due to heterogeneity within the host. Unfortunately, due to a host homogeneity assumption in the microbial dose-response models' derivation, the current QMRA method of modeling exposure volume heterogeneity is not an accurate method for pathogens such as Legionella pneumophila. Therefore, a new method to model within-group heterogeneity is needed. The method developed in this research uses USA national incidence rates from the Centers for Disease Control and Prevention (CDC) to calculate proxies for the morbidity ratio that are descriptive of the within-group variability. From these proxies, an example QMRA model is developed to demonstrate their use. This method makes the QMRA results more representative of clinical outcomes and increases population-specific precision. Further, the risks estimated demonstrate a significant difference between demographic groups known to have heterogeneous health outcomes after infection. The method both improves fidelity to the real health impacts resulting from L. pneumophila infection and allows for the estimation of severe disability-adjusted life years (DALYs) for Legionnaires' disease, moderate DALYs for Pontiac fever, and post-acute DALYs for sequela after recovering from Legionnaires' disease.
    • Assimilation of Satellite-Based Data for Hydrological Mapping of Precipitation and Direct Runoff Coefficient for the Lake Urmia Basin in Iran

      Akbari, Mahdi; Haghighi, Ali Torabi; Aghayi, Mohammad Mahdi; Javadian, Mostafa; Tajrishy, Masoud; Klove, Bjorn; Univ Arizona, Dept Hydrol & Atmospher Sci (MDPI, 2019-08)
      Water management in arid basins often lacks sufficient hydro-climatological data because, e.g., rain gauges are typically absent at high elevations and inflow to ungauged areas around large closed lakes is difficult to estimate. We sought to improve precipitation and runoff estimation in an arid basin (Lake Urmia, Iran) using methods involving assimilation of satellite-based data. We estimated precipitation using interpolation of rain gauge data by kriging, downscaling the Tropical Rainfall Measuring Mission (TRMM), and cokriging interpolation of in-situ records with Remote Sensing (RS)-based data. Using RS-based data application in estimations gave more precise results, by compensating for lack of data at high elevations. Cokriging interpolation of rain gauges by TRMM and Digitized Elevation Model (DEM) gave 4-9 mm lower Root Mean Square Error (RMSE) in different years compared with kriging. Downscaling TRMM improved its accuracy by 14 mm. Using the most accurate precipitation result, we modeled annual direct runoff with Kennessey and Soil Conservation Service Curve Number (SCS-CN) models. These models use land use, permeability, and slope data. In runoff modeling, Kennessey gave higher accuracy. Calibrating Kennessey reduced the Normalized RMSE (NRMSE) from 1 in the standard model to 0.44. Direct runoff coefficient map by 1 km spatial resolution was generated by calibrated Kennessey. Validation by the closest gauges to the lake gave a NRMSE of 0.41 which approved the accuracy of modeling.
    • Coastal California Wastewater Effluent as a Resource for Seawater Desalination Brine Commingling

      Rodman, Kelly; Cervania, Ahron; Budig-Markin, Valerie; Schermesser, Cory; Rogers, Oliver; Martinez, Joshua; King, Julia; Hassett, Patrick; Burns, Jacob; Gonzales, Malia; et al. (MDPI, 2018-03)
      California frequently experiences water scarcity, especially in high population areas. This has generated increased interest in using the Pacific Ocean as a water resource, with seawater desalination becoming a popular solution. To mitigate the environmental impacts of the high salinity brine from seawater desalination, California recommends commingling brine with wastewater effluent before ocean discharge. Results reveal that throughout the California coast, approximately 4872 MLD (1287 MGD) of treated wastewater are discharged into the ocean and might be available as dilution water. Most of this dilution water resource is produced in Southern California (3161 MLD or 835 MGD) and the San Francisco Bay Area (1503 MLD or 397 MGD), which are also the areas with the highest need for alternative water sources. With this quantity of dilution water, in principle, over 5300 MLD (1400 MGD) of potable water could be produced in California through seawater desalination. Furthermore, this study provides a survey of the treatment levels and typical discharge violations of ocean wastewater treatment facilities in California.
    • Collaborative, Risk-Informed, Triple Bottom Line, Multi-Criteria Decision Analysis Planning Framework for Integrated Urban Water Management

      Cole, Jeanne; Sharvelle, Sybil; Grigg, Neil; Pivo, Gary; Haukaas, Jon; Univ Arizona, Coll Architecture Planning & Landscape Architectu (MDPI, 2018-12)
      The historical division of water management into different sectors, with financially and technologically driven decision processes, makes taking a more holistic approach to finding sustainable solutions for urban water management difficult. Here, a planning framework for Integrated Urban Water Management (IUWM) that evolved during a two-year study evaluating alternative strategies for dual water supply within a local government context is described. The planning framework was developed to overcome the obstacles that surfaced over the course of the study. It provides a structured approach to strategic decision making that integrates triple bottom line (TBL), multi-criteria decision analysis (MCDA), uncertainty and sensitivity analyses, and participatory decision making into an exploration of water supply alternatives. TBL assured stakeholders that the decisions considered the financial, social, and environmental performance. MCDA provided visibility into the benefits and trade-offs of the alternatives by providing a quantitative method for comparing alternatives that incorporates incommensurate performance indicators and priorities of multiple stakeholders. Uncertainty and sensitivity analyses addressed concerns regarding decision risk and improved transparency into inputs driving uncertainty in the analysis. Finally, a flexible participatory process helped to circumvent socio-institutional barriers by adapting the methodology and increasing cooperation among stakeholders and multidisciplinary experts. The resulting collaborative, risk-informed, TBL-MCDA (CRTM) planning framework helps to refine the feasible set of alternatives by providing more transparency into the drivers, technologies, and stakeholders influencing the decision. The planning framework increased the number of participants that were involved in the study, increased interaction between participants, changed the structure of the decision problem, increased the number of performance indicators considered, and improved stakeholder cooperation in the decision process.
    • Drought Propagation in Semi-Arid River Basins in Latin America: Lessons from Mexico to the Southern Cone

      Oertel, Melanie; Meza, Francisco; Gironás, Jorge; A. Scott, Christopher; Rojas, Facundo; Pineda-Pablos, Nicolás; Univ Arizona, Udall Ctr Studies Publ Policy; Univ Arizona, Sch Geog & Dev (MDPI, 2018-11)
      Detecting droughts as early as possible is important in avoiding negative impacts on economy, society, and environment. To improve drought monitoring, we studied drought propagation (i.e., the temporal manifestation of a precipitation deficit on soil moisture and streamflow). We used the Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Streamflow Index (SSI), and Standardized Soil Moisture Index (SSMI) in three drought-prone regions: Sonora (Mexico), Maipo (Chile), and Mendoza-Tunuyan (Argentina) to study their temporal interdependence. For this evaluation we use precipitation, temperature, and streamflow data from gauges that are managed by governmental institutions, and satellite-based soil moisture from the ESA CCI SM v03.3 combined data set. Results confirm that effective drought monitoring should be carried out (1) at river-basin scale, (2) including several variables, and (3) considering hydro-meteorological processes from outside its boundaries.
    • Event-Response Ellipses: A Method to Quantify and Compare the Role of Dynamic Storage at the Catchment Scale in Snowmelt-Dominated Systems

      Driscoll, Jessica; Meixner, Thomas; Molotch, Noah; Ferre, Ty; Williams, Mark; Sickman, James; Univ Arizona, Dept Hydrol & Water Resources (MDPI, 2018-12)
      A method for quantifying the role of dynamic storage as a physical buffer between snowmelt and streamflow at the catchment scale is introduced in this paper. The method describes a quantitative relation between hydrologic events (e.g., snowmelt) and responses (e.g., streamflow) by generating event-response ellipses that can be used to (a) characterize and compare catchment-scale dynamic storage processes, and (b) assess the closure of the water balance. Event-response ellipses allow for the role of dynamic, short-term storage to be quantified and compared between seasons and between catchments. This method is presented as an idealization of the system: a time series of a snowmelt event as a portion of a sinusoidal wave function. The event function is then related to a response function, which is the original event function modified mathematically through phase and magnitude shifts to represent the streamflow response. The direct relation of these two functions creates an event-response ellipse with measurable characteristics (e.g., eccentricity, angle). The ellipse characteristics integrate the timing and magnitude difference between the hydrologic event and response to quantify physical buffering through dynamic storage. Next, method is applied to eleven snowmelt seasons in two well-instrumented headwater snowmelt-dominated catchments with known differences in storage capacities. Results show the time-period average daily values produce different event-response ellipse characteristics for the two catchments. Event-response ellipses were also generated for individual snowmelt seasons; however, these annual applications of the method show more scatter relative to the time period averaged values. The event-response ellipse method provides a method to compare and evaluate the connectivity between snowmelt and streamflow as well as assumptions of water balance.
    • Fine Characterization of the Effects of Aquifer Heterogeneity on Solute Transport: A Numerical Sandbox Experiment

      Zhang, Yuefen; Wu, Chuanhao; Hu, Bill X; Yeh, Tian-Chyi Jim; Hao, Yimin; Lv, Wenhan; Univ Arizona, Dept Hydrol & Water Resources (MDPI, 2019-11-01)
      Hydraulic conductivity (K) and the specific storage coefficient (S) are among the most important hydrogeological parameters of an aquifer. Traditionally, the hydrogeological parameters of a field aquifer system are mainly determined through a range of experiments that are both time-consuming and of poor operability. To accurately characterize aquifer heterogeneity, a synthetic sandbox is constructed using VSAFT2 (Variably Saturated Flow and Transport utilizing the Modified Method of Characteristics, in 2D) as a reference aquifer system by incorporating multilevel a priori geologic information into the sandbox configuration. The spatial distribution of the field of hydraulic conductivity (i.e., K) is inversely obtained by hydraulic tomography (HT). Then HT is compared with traditional kriging-estimated method in the fine characterization of aquifer heterogeneity, and the optimal K field is eventually selected to predict the solute transport. The influence of the number of pumping cycles on the accuracy of heterogeneity characterization is also discussed. The results show that the accuracy of the inversely obtained K field is improved with the increased number of pumping cycles. When incorporating multilevel a priori geological information, HT can characterize aquifer heterogeneity more finely than traditional kriging, and there is also a very good fitting of solute transport between the optimally estimated K field and the reference K field. Our study highlights the importance of the fine characterization of aquifer heterogeneity for the prediction of solute transport.
    • The First Drying Lake in Chile: Causes and Recovery Options

      Valdés-Pineda, Rodrigo; García-Chevesich, Pablo; Valdés, Juan B.; Pizarro-Tapia, Roberto; Univ Arizona, Hydrol & Atmospher Sci Dept (MDPI, 2020-01-19)
      Located southwest of the city of Santiago (Chile), the Aculeo Lagoon used to be an important body of water, providing environmental, social, and economic services to both locals (mostly drinking water and small-scale agricultural irrigation) and tourists who visited the area for fishing, sailing, and other recreational activities. The lagoon dried completely in May of 2018. The phenomenon has been attributed to the current climatic drought. We implemented and calibrated a surface-groundwater model to evaluate the hydrogeologic causes of the lagoon's disappearance, and to develop feasible solutions. The lagoon's recovery requires a series of urgent actions, including environmental education and significant investment in infrastructure to import water. Ultimately, there are two goals: bringing back historic water levels and ensuring the sustainability of water resources at the catchment scale.
    • Investigation of Karst Spring Flow Cessation Using Grey System Models

      Guo, Yaru; Yeh, Tian-Chyi Jim; Hao, Yonghong; Univ Arizona, Dept Hydrol & Water Resources (MDPI, 2019-09-15)
      Karst aquifers are prominent sources of water worldwide; they store large amounts of water and are known for their beautiful springs. However, extensive groundwater development and climate variation has resulted in a decline in the flow of most karst springs; some have even dried up. In order to obtain a better understanding of the factors contributing to this development, this study introduced grey system models, which quantified spring flow, taking Jinci Springs (China), which dried up in May 1994, as an example. Based on the characteristics of Jinci Springs, spring flow was divided into two stages: first (1954–1960), when the spring flow was affected only by climate variation; and second (1961–1994), when the flow was impacted by both climate variation and anthropogenic activities. The results showed that Jinci Springs flow had a strong relationship with precipitation occurring one year and three years earlier in the first stage. Subsequently, a grey system GM (1,3) model with one-year and three-year lags was set up for the first stage. By using the GM (1,3) model, we simulated the spring flow in the second stage under effects of climate variation only. By subtracting the observed spring flow from the simulated flow, we obtained the contribution of anthropogenic activities to Jinci Springs’ cessation. The contribution of anthropogenic activities and climate variation to the decline was 1.46 m3/s and 0.62 m3/s, respectively. Finally, each human activity that caused the decline was estimated. The methods devised herein can be used to describe karst hydrological processes that are under the effects of anthropogenic activities and climate variation.
    • Legionella pneumophila as a Health Hazard to Miners: A Pilot Study of Water Quality and QMRA

      Madera-García, Valerie; Mraz, Alexis L.; López-Gálvez, Nicolás; Weir, Mark H.; Werner, James; Beamer, Paloma I.; Verhougstraete, Marc P.; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth, Dept Commun Environm & Policy (MDPI, 2019-08)
      Legionella pneumophila (L. pneumophila), the causative agent of legionellosis, is an aquatic bacterium that grows in warm water. Humans are only presented with a health risk when aerosolized water containing L. pneumophila is inhaled. In mining operations, aerosolized water is used as dust control and as part of the drilling operations, a currently ignored exposure route. This study characterized L. pneumophila concentrations in the mine's non-potable water and the relationship between L. pneumophila and chlorine concentrations. These concentrations informed a quantitative microbial risk assessment (QMRA) model to estimate the infection risk to miners exposed to aerosolized water containing L. pneumophila. Fourteen water samples were collected from seven locations at a mine and analyzed for temperature, pH, chlorine, and L. pneumophila serogroup. Most samples (93%) tested positive for L. pneumophila cells. The faucet from the sprinkler system on the adit level (entrance to the underground mine levels) showed the highest concentration of L. pneumophila (8.35 x 10(4) MPN/L). Disability adjusted life years (DALYs) were estimated in the QMRA model and showed that the risk for all miners was significantly lower (p < 0.0001) with the ventilation system on than when the system was off. Our study showed that the use of a ventilation system at the adit level of the mine reduced the risk of infection with aerosolized L. pneumophila.
    • Long-Term Storage Credits: Analyzing Market-Based Transactions to Achieve Arizona Water Policy Objectives

      Bernat, Rebecca F. A.; Megdal, Sharon B.; Eden, Susanna; Univ Arizona, Coll Agr & Life Sci, Dept Environm Sci; Univ Arizona, Water Resources Res Ctr, Coll Agr & Life Sci (MDPI, 2020-02-19)
      The state of Arizona has created a unique water management tool in response to water scarcity and population growth. In 1994, Arizona's state legislature authorized the creation of long-term storage credits (LTSCs) through aquifer recharge with Colorado River water or effluent. LTSCs represent a quantity of water the owner is entitled to recover and use once the water has remained underground for a full calendar year. Owners may also sell their LTSCs to others by a simple credit account transfer. LTSCs have emerged as a tool for water users to achieve compliance with groundwater regulations in the most populated areas of the state, such as the cities of Phoenix and Tucson. Using data collected and maintained by the state's water resources regulator, this study examines sales of LTSCs to reveal patterns of market-based transactions. Analysis of 23 years of public records shows several trends: (1) LTSC transactions have been increasing since 2003; (2) municipal water providers and investment firms have been active participants in LTSC transactions; (3) the greatest transaction volumes involve governmental entities established by state law with groundwater recharge and replenishment obligations. This analysis reveals how LTSCs have contributed to achieving water policy goals in Central Arizona and suggests how the LTSC system can be used to improve water use efficiency through voluntary redistribution in other water scarce regions.
    • METRIC and WaPOR Estimates of Evapotranspiration over the Lake Urmia Basin: Comparative Analysis and Composite Assessment

      Javadian, Mostafa; Behrangi, Ali; Gholizadeh, Mohsen; Tajrishy, Masoud; Univ Arizona, Dept Hydrol & Atmospher Sci (MDPI, 2019-08)
      Evapotranspiration is one of the main components of water and energy balance. In this study, we compare two ET products, suitable for regional analysis at high spatial resolution: The recent WaPOR product developed by FAO and METRIC algorithm. WaPOR is based on ETLook, which is a two-source model and relies on microwave images. WaPOR is unique as it has no limitation under cloudy days, but METRIC is limited by clouds. METRIC and WaPOR are more sensitive to land surface temperature and soil moisture, respectively. Using two years (2010 and 2014) of data over Lake Urmia basin, we show that in most areas, ET from METRIC is higher than WaPOR and the difference has an ascending trend with the elevation. The ET of lysimeter station is fairly consistent with METRIC based on a single observation. Our analysis using NDVI and land use maps suggests that the histogram of ET from WaPOR might be more realistic than METRIC, but not its amount. The fraction of ET to precipitation in rainfed agriculture areas shows that WaPOR is more accurate than METRIC, mainly because in the absence of other water resources such as ground water annual ET cannot exceed annual precipitation. In contrast, METRIC produces a more realistic estimate than WaPOR over irrigated farms. The results suggest that the two products can complement each other.
    • Modeling Riparian Restoration Impacts on the Hydrologic Cycle at the Babacomari Ranch, SE Arizona, USA

      Norman, Laura; Callegary, James; Lacher, Laurel; Wilson, Natalie; Fandel, Chloé; Forbes, Brandon; Swetnam, Tyson; Univ Arizona, Hydrol & Atmospher Sci; Univ Arizona, BIO5 Inst (MDPI, 2019-02)
      This paper describes coupling field experiments with surface and groundwater modeling to investigate rangelands of SE Arizona, USA using erosion-control structures to augment shallow and deep aquifer recharge. We collected field data to describe the physical and hydrological properties before and after gabions (caged riprap) were installed in an ephemeral channel. The modular finite-difference flow model is applied to simulate the amount of increase needed to raise groundwater levels. We used the average increase in infiltration measured in the field and projected on site, assuming all infiltration becomes recharge, to estimate how many gabions would be needed to increase recharge in the larger watershed. A watershed model was then applied and calibrated with discharge and 3D terrain measurements, to simulate flow volumes. Findings were coupled to extrapolate simulations and quantify long-term impacts of riparian restoration. Projected scenarios demonstrate how erosion-control structures could impact all components of the annual water budget. Results support the potential of watershed-wide gabion installation to increase total aquifer recharge, with models portraying increased subsurface connectivity and accentuated lateral flow contributions.
    • Optimization Difficulty Indicator and Testing Framework for Water Distribution Network Complexity

      Jung, Donghwi; Lee, Seungyub; Hwang, Hwee; Univ Arizona, Dept Civil & Architectural Engn & Mech (MDPI, 2019-10-14)
      In the last three decades, benchmark water distribution networks (WDNs) have provided a common testbed for new optimization algorithms and design approaches. However, deriving generalized and reliable conclusions from such benchmark WDNs is difficult because their optimization difficulty levels (ODLs) are either too low or too high (i.e., biased). Final solutions do not consistently converge to a global optimum for a WDN problem with a high ODL. In addition, little effort has been given to quantifying and comparing the ODLs of WDNs with different characteristics and conditions. In this study, an ODL indicator was developed for WDNs: the coefficient of variation of the final solution fitness values. An ODL quantification framework was also developed with two phases: (1) generating network layouts with various topological characteristics, and (2) quantifying the statistics of the final solution quality and ODL by using a global parallel genetic algorithm. The proposed indicator and framework were applied to the design of a dense-grid B-city network and large C network, and the results demonstrated their applicability to generating a WDN benchmark problem with the target ODL.
    • An Overview of Managed Aquifer Recharge in Mexico and Its Legal Framework

      Cruz-Ayala, Mary Belle; Megdal, Sharon B.; Univ Arizona, Water Resources Res Ctr; Univ Arizona (MDPI, 2020-02-10)
      In Mexico, one hundred of the 188 most important aquifers dedicated to agriculture and human consumption are over-exploited and 32 are affected by seawater intrusion in coastal areas. Considering that Mexico relies on groundwater, it is vital to develop a portfolio of alternatives to recover aquifers and examine policies and programs regarding reclaimed water and stormwater. Managed Aquifer Recharge (MAR) may be useful for increasing water availability and adapting to climate change in semi-arid regions of Mexico. In this paper, we present an overview of water recharge projects that have been conducted in Mexico in the last 50 years, their methods for recharge, water sources, geographical distribution, and the main results obtained in each project. We found three types of MAR efforts: (1) exploratory and suitability studies for MAR, (2) pilot projects, and (3) MAR facilities that currently operate. This study includes the examination of the legal framework for MAR to identify some challenges and opportunities that Mexican regulation contains in this regard. We find that beyond the technical issues that MAR projects normally address, the regulatory framework is a barrier to increasing MAR facilities in Mexico.
    • Phreatic Water Quality Assessment and Associated Hydrogeochemical Processes in an Irrigated Region Along the Upper Yellow River, Northwestern China

      Liu, Fei; Zhao, Zhipeng; Yang, Lihu; Ma, Yuxue; Li, Bingliang; Gong, Liang; Liu, Haiyan; Univ Arizona, Dept Hydrol & Atmospher Sci (MDPI, 2020-02-10)
      Groundwater resources are playing an increasingly vital role in water supply for domestic and irrigation purposes in the Yinchuan Plain, along with the reduction in water transfer from the Yellow River. This study aimed to identify the current status of phreatic water quality and associated hydrogeochemical processes in an irrigated region along the upper Yellow River. A total of 78 water samples were collected in September 2018 for chemical analysis. Results showed that the phreatic water was excellent or good in most areas west of the Yellow River, while it was poor or very poor quality in some places east of the Yellow River. The nitrate contamination is particularly severe in the pluvial-alluvial plain, relating to the localized fine-grained zone with low permeability. Most samples had no sodium hazard but had magnesium hazard. Additionally, the overall evolutionary trend of the phreatic water showed the transformation of Ca-Mg-HCO3 into Na-Cl-SO4 type. Rock weathering and evaporation jointly predominate the evolution of phreatic water chemistry. The main geochemical processes involve the dissolution/precipitation of gypsum, halite, dolomite. and calcite, along with the cation exchange. Insights from this work have important implications for groundwater sustainable management in such irrigated regions along the upper Yellow River.
    • Probabilistic Analysis of Extreme Discharges and Precipitations with a Nonparametric Copula Model

      Liu, Yan; Liu, Youcun; Hao, Yonghong; Wang, Tongke; Yeh, Tian-Chyi; Fan, Yonghui; Zhang, Qiaozhen; Univ Arizona, Dept Hydrol & Water Resources (MDPI, 2018-07)
      Urumqi River is an important river in the Xinjiang autonomous region, China, where floods or droughts are the major concerns of the local communities. This river's discharge is mainly influenced by the natural factors such as precipitation and climates, rather than human activities. This paper quantifies the interdependent structure between Urumqi River's discharge and precipitation using a nonparametric Copula method. It then analyzes the relationship between the extreme discharges of this river and extreme precipitation of the region. Comparison between simulation result and real data is conducted to verify the rationality of the model. Furthermore, the conditional probabilities of maximum and minimum discharge at different precipitation levels are also investigated using the Copula distribution functions. The results show a strong relationship between large discharge and heavy precipitation in this region. The upper dependence coefficient is nearly 0.6 and the probability of large discharge reaches 0.64 when the rainfall is greater than 159.56 mm. The relationship between small discharge and rainfall is insignificant. The lower dependence coefficient is zero, suggesting that the base flow and snowmelt from Tianshan likely contribute to Urumqi River's discharge during the dry season.
    • Quantifying the Impact of Climate Change and Human Activities on Streamflow in a Semi-Arid Watershed with the Budyko Equation Incorporating Dynamic Vegetation Information

      Tian, Lei; Jin, Jiming; Wu, Pute; Niu, Guo-Yue; Univ Arizona, Biosphere 2; Univ Arizona, Dept Hydrol & Atmospher Sci (MDPI, 2018-12)
      Understanding hydrological responses to climate change and land use and land cover change (LULCC) is important for water resource planning and management, especially for water-limited areas. The annual streamflow of the Wuding River Watershed (WRW), the largest sediment source of the Yellow River in China, has decreased significantly over the past 50 years at a rate of 5.2 mm/decade. Using the Budyko equation, this study investigated this decrease with the contributions from climate change and LULCC caused by human activities, which have intensified since 1999 due to China's Grain for Green Project (GFGP). The Budyko parameter that represents watershed characteristics was more reasonably configured and derived to improve the performance of the Budyko equation. Vegetation changes were included in the Budyko equation to further improve its simulations, and these changes showed a significant upward trend due to the GFGP based on satellite data. An improved decomposition method based on the Budyko equation was used to quantitatively separate the impact of climate change from that of LULCC on the streamflow in the WRW. Our results show that climate change generated a dominant effect on the streamflow and decreased it by 72.4% in the WRW. This climatic effect can be further explained with the drying trend of the Palmer Severity Drought Index, which was calculated based only on climate change information for the WRW. In the meantime, although human activities in this watershed have been very intense, especially since 1999, vegetation cover increase contributed a 27.6% decline to the streamflow, which played a secondary role in affecting hydrological processes in the WRW.
    • Transient Hydraulic Tomography Analysis of Fourteen Pumping Tests at a Highly Heterogeneous Multiple Aquifer–Aquitard System

      Zhao, Zhanfeng; Illman, Walter A.; Zha, Yuanyuan; Yeh, Tian-Chyi Jim; Mok, Chin Man Bill; Berg, Steven J.; Han, Dongmei; Univ Arizona, Dept Hydrol & Atmospher Sci (MDPI, 2019-09-08)
      Hydraulic tomography based on geostatistics has proven to be robust in characterizing subsurface heterogeneity in hydraulic conductivity (K) and specific storage (S-s) through the joint inversion of drawdown records from multiple pumping tests. However, the spatially variable estimates can be smooth or even erroneous for areas where pumping/observation data densities are not high. Previous hydraulic tomography surveys conducted at the North Campus Research Site (NCRS) on the University of Waterloo campus in Waterloo, Canada, revealed that the estimated hydraulic parameters were smooth and the known aquitard was erroneously identified as a high K zone. This was likely the consequence of the site being highly heterogeneous, while only utilizing four pumping tests and not having measurable drawdowns in the low K aquitard for inverse modeling. Here, we investigate whether improved K and S-s estimates could be obtained through the inclusion of additional pumping test data by stressing both aquifer and aquitard zones for a sufficiently long period. Specifically, six additional pumping/injection tests were conducted at the site, and a transient hydraulic tomography analysis with 14 tests was completed. Results reveal that there is a significant improvement to the K and S-s tomograms in terms of the visual correspondence with various geologic units, including its connectivity. More importantly, with the availability of additional data, we found that the inverse model now can better capture the high and low K features for nine boreholes when compared with K values obtained from permeameter tests. The estimated K and S-s tomograms are then used for the forward simulation of one additional pumping test not used for model calibration, revealing reasonable predictions. While encouraging results are obtained by including a large number of pumping tests to the transient hydraulic tomography analysis, stratigraphic boundaries are still smoothed, which is a direct consequence of utilizing a geostatistics-based inversion approach that assumes stationarity in statistical properties. To capture such sharp boundaries, incorporation of additional data types, such as geological and geophysical information, may be necessary when data densities are not sufficiently high.
    • Ubiquitous Fractal Scaling and Filtering Behavior of Hydrologic Fluxes and Storages from A Mountain Headwater Catchment

      Dwivedi, Ravindra; Knowles, John F.; Eastoe, Christopher; Minor, Rebecca; Abramson, Nathan; Mitra, Bhaskar; Wright, William E.; McIntosh, Jennifer; Meixner, Thomas; “Ty” Ferre, Paul A.; et al. (MDPI, 2020-02-24)
      We used the weighted wavelet method to perform spectral analysis of observed long-term precipitation, streamflow, actual evapotranspiration, and soil water storage at a sub-humid mountain catchment near Tucson, Arizona, USA. Fractal scaling in precipitation and the daily change in soil water storage occurred up to a period of 14 days and corresponded to the typical duration of relatively wet and dry intervals. In contrast, fractal scaling could be observed up to a period of 0.5 years in streamflow and actual evapotranspiration. By considering long-term observations of hydrologic fluxes and storages, we show that, in contrast to previous findings, the phase relationships between water balance components changed with component period and were not perfectly in or out of phase at all periods. Self-averaging behavior was apparent, but the temporal scales over which this behavior was applicable differed among the various water balance components. Conservative tracer analysis showed that this catchment acted as a fractal filter by transforming white noise in the precipitation input signal to a 1/f flicker in the streamflow output signal by means of both spatial and temporal subsurface advection and dispersion processes and soil wetting properties. This study provides an improved understanding of hydrological filtering behavior in mountain critical zones that are critical sources of water and ecosystem services throughout the world.