- Professor, Hydrology and Water Resources
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Appl Groundwater ModelHWRS 482 (Spring 2017)
Appl Groundwater ModelHWRS 582 (Spring 2017)
Appl Groundwater ModelHWRS 482 (Spring 2016)
Appl Groundwater ModelHWRS 582 (Spring 2016)
ResearchHWRS 900 (Spring 2016)
- Ajami, H., Maddock, T., Meixner, T., Hogan, J. F., & Guertin, D. P. (2012). RIPGIS-NET: A GIS tool for Riparian Groundwater Evapotranspiration in MODFLOW. Ground Water, 50(1), 154-158.More infoPMID: 21385181;Abstract: RIPGIS-NET, an Environmental System Research Institute (ESRI's) ArcGIS 9.2/9.3 custom application, was developed to derive parameters and visualize results of spatially explicit riparian groundwater evapotranspiration (ETg), evapotranspiration from saturated zone, in groundwater flow models for ecohydrology, riparian ecosystem management, and stream restoration. Specifically RIPGIS-NET works with riparian evapotranspiration (RIP-ET), a modeling package that works with the MODFLOW groundwater flow model. RIP-ET improves ETg simulations by using a set of eco-physiologically based ETg curves for plant functional subgroups (PFSGs), and separates ground evaporation and plant transpiration processes from the water table. The RIPGIS-NET program was developed in Visual Basic 2005, NET framework 2.0, and runs in ArcMap 9.2 and 9.3 applications. RIPGIS-NET, a pre- and post-processor for RIP-ET, incorporates spatial variability of riparian vegetation and land surface elevation into ETg estimation in MODFLOW groundwater models. RIPGIS-NET derives RIP-ET input parameters including PFSG evapotranspiration curve parameters, fractional coverage areas of each PFSG in a MODFLOW cell, and average surface elevation per riparian vegetation polygon using a digital elevation model. RIPGIS-NET also provides visualization tools for modelers to create head maps, depth to water table (DTWT) maps, and plot DTWT for a PFSG in a polygon in the Geographic Information System based on MODFLOW simulation results. © 2011, The Author(s). Ground Water © 2011, National Ground Water Association.
- Ajami, H., Meixner, T., Dominguez, F., Hogan, J., & Maddock, T. (2012). Seasonalizing Mountain System Recharge in Semi-Arid Basins-Climate Change Impacts. Ground Water, 50(4), 585-597.More infoPMID: 22091994;Abstract: Climate variability and change impact groundwater resources by altering recharge rates. In semi-arid Basin and Range systems, this impact is likely to be most pronounced in mountain system recharge (MSR), a process which constitutes a significant component of recharge in these basins. Despite its importance, the physical processes that control MSR have not been fully investigated because of limited observations and the complexity of recharge processes in mountainous catchments. As a result, empirical equations, that provide a basin-wide estimate of mean annual recharge using mean annual precipitation, are often used to estimate MSR. Here North American Regional Reanalysis data are used to develop seasonal recharge estimates using ratios of seasonal (winter vs. summer) precipitation to seasonal actual or potential evapotranspiration. These seasonal recharge estimates compared favorably to seasonal MSR estimates using the fraction of winter vs. summer recharge determined from isotopic data in the Upper San Pedro River Basin, Arizona. Development of hydrologically based seasonal ratios enhanced seasonal recharge predictions and notably allows evaluation of MSR response to changes in seasonal precipitation and temperature because of climate variability and change using Global Climate Model (GCM) climate projections. Results show that prospective variability in MSR depends on GCM precipitation predictions and on higher temperature. Lower seasonal MSR rates projected for 2050-2099 are associated with decreases in summer precipitation and increases in winter temperature. Uncertainty in seasonal MSR predictions arises from the potential evapotranspiration estimation method, the GCM downscaling technique and the exclusion of snowmelt processes. © 2011, The Author(s). Ground Water © 2011, National Ground Water Association.
- Ajami, H., Meixner, T., III, T. M., Hogan, J. F., & Guertin, D. P. (2011). Impact of land-surface elevation and riparian evapotranspiration seasonality on groundwater budget in MODFLOW models. Hydrogeology Journal, 19(6), 1181-1188.More infoAbstract: Riparian groundwater evapotranspiration (ETg) constitutes a major component of the water balance especially in many arid and semi-arid environments. Although spatial and temporal variability of riparian ETg are controlled by climate, vegetation and subsurface characteristics, depth to water table (DTWT) is often considered the major controlling factor. Relationships between ETg rates and DTWT, referred to as ETg curves, are implemented in MODFLOW ETg packages (EVT, ETS1 and RIP-ET) with different functional forms. Here, the sensitivity of the groundwater budget in MODFLOW groundwater models to ETg parameters (including ETg curves, land-surface elevation and ETg seasonality) are investigated. A MODFLOW model of the hypothetical Dry Alkaline Valley in the Southwestern USA is used to show how spatial representation of riparian vegetation and digital elevation model (DEM) processing methods impact the water budget when RIPGIS-NET (a GIS-based ETg program) is used with MODFLOW's RIP-ET package, and results are compared with the EVT and ETS1 packages. Results show considerable impact on ETg and other groundwater budget components caused by spatial representation of riparian vegetation, vegetation type, fractional coverage areas and land-surface elevation. RIPGIS-NET enhances ETg estimation in MODFLOW by incorporating vegetation and land-surface parameters, providing a tool for ecohydrology studies, riparian ecosystem management and stream restoration. © 2011 Springer-Verlag.
- Ajami, H., Troch, P. A., III, T. M., Meixner, T., & Eastoe, C. (2011). Quantifying mountain block recharge by means of catchment-scale storage-discharge relationships. Water Resources Research, 47(4).More infoAbstract: Despite the importance of mountainous catchments for providing freshwater resources, especially in semi-arid regions, little is known about key hydrological processes such as mountain block recharge (MBR). Here we implement a data-based method informed by isotopic data to quantify MBR rates using recession flow analysis. We applied our hybrid method in a semi-arid sky island catchment in southern Arizona, United States. Sabino Creek is a 91 km 2 catchment with its sources near the summit of the Santa Catalina Mountains northeast of Tucson. Southern Arizona's climate has two distinct wet seasons separated by prolonged dry periods. Winter frontal storms (November-March) provide about 50% of annual precipitation, and summers are dominated by monsoon convective storms from July to September. Isotope analyses of springs and surface water in the Sabino Creek catchment indicate that streamflow during dry periods is derived from groundwater storage in fractured bedrock. Storage-discharge relationships are derived from recession flow analysis to estimate changes in storage during wet periods. To provide reliable estimates, several corrections and improvements to classic base flow recession analysis are considered. These corrections and improvements include adaptive time stepping, data binning, and the choice of storage-discharge functions. Our analysis shows that (1) incorporating adaptive time steps to correct for streamflow measurement errors improves the coefficient of determination, (2) the quantile method is best for streamflow data binning, (3) the choice of the regression model is critical when the stage-discharge function is used to predict changes in bedrock storage beyond the maximum observed flow in the catchment, and (4) the use of daily or night-time hourly streamflow does not affect the form of the storage-discharge relationship but will impact MBR estimates because of differences in the observed range of streamflow in each series. Copyright 2011 by the American Geophysical Union.
- Valdes, J., & Maddock, T. (2010). Conjunctive water management in the US southwest. Water and Sustainability in Arid Regions: Bridging the Gap Between Physical and Social Sciences, 221-244.More infoAbstract: Water demands in the US Southwest have been subject to great pressures due to explosive population growth and climate variability that has produced decadal droughts. These pressures have led to unsustainable use of surface water and groundwater, forcing states to adopt conjunctive management of ground and surface water systems. Unfortunately, federal and state laws have not kept pace with the scientific development of management strategies. A series of examples are presented to illustrate some successes and failures of integration of surface water and groundwater management and its accompanying legal implications. © 2010 Springer Science+Business Media B.V.
- Whittier, J., & III, T. M. (2006). Groundwater flow model of the Lower San Pedro River basin for the sustainability of riparian habitats. IAHS-AISH Publication, 59-66.More infoAbstract: Water issues in the Lower San Pedro River (SPR) basin are becoming increasingly contentious as human activity competes with sustainability of the riparian habitat. The SPR flows north from Sonora, Mexico to its confluence with the Gila River in Arizona, USA. In order to better understand the water demands in this basin, a new groundwater flow model was created simulating conditions prior to 1940 and changes from 1940 to 2000. The model results project potential impacts to the sustainability of groundwater within the basin. Natural indicators show downward trends involving declines in water table levels near the river due to pumping, underflow to the Gila River basin, water available for sustaining riparian vegetation, water available in storage, and flow from the aquifer to the river. In the future, the model will be used as an administrative tool to assess alternative land management scenarios and their abilities to sustain or improve the riparian habitat.
- Baird, K. J., & III, T. M. (2005). Simulating riparian evapotranspiration: A new methodology and application for groundwater models. Journal of Hydrology, 312(1-4), 176-190.More infoAbstract: This paper describes the development and application of a new methodology to simulate riparian and wetland evapotranspiration (ET) in groundwater models. Traditional approaches for modeling ET are based on quasi-linear relationship between ET flux rate and hydraulic head (groundwater elevation). The approach presented here uses multiple non-linear, segmented flux curves that reflect the ecophysiology of the plant species in these systems. Five plant functional groups (PFGs) based on water tolerance ranges and rooting depths are used to elucidate the interactive processes of plant transpiration with groundwater conditions. ET flux rate curves set the extinction and saturation extinction depths and define the group's ET flux rate as a function of water table depth relative to the ground surface. The calculated ET loss from a riparian or wetland system is dependent on the contributing area of each plant functional subgroup present and water table conditions. The new methodology requires a fractional coverage for each of the PFGs present within the groundwater model cell and allows for more accurate assignment of land surface elevations. Model results for a case-study show significant differences in predicted ET and subsequent depth to groundwater between the new and the traditional approaches. The development of physiologically based transpiration curves combined with the traditional linear curve for bare soil/open water results in more accurate determinations of riparian ET and improved basin scale water budgets. The use of PFGs in combination with the new RIP-ET package provides an explicit link between groundwater and riparian/wetland habitat conditions and offers an opportunity to better manage and restore riparian and wetland systems. © 2005 Elsevier B.V. All rights reserved.
- Baird, K. J., Stromberg, J. C., & III, T. M. (2005). Linking riparian dynamics and groundwater: An ecohydrologic approach to modeling groundwater and riparian vegetation. Environmental Management, 36(4), 551-564.More infoPMID: 16222461;Abstract: The growing use of global freshwater supplies is increasing the need for improved modeling of the linkage between groundwater and riparian vegetation. Traditional groundwater models such as MODFLOW have been used to predict changes in regional groundwater levels, and thus riparian vegetation potential attributable to anthropogenic water use. This article describes an approach that improves on these modeling techniques through several innovations. First, evapotranspiration from riparian/wetland systems is modeled in a manner that more realistically reflects plant ecophysiology and vegetation complexity. In the authors' model programs (RIP-ET and PRE-RIP-ET), the single, monotonically increasing evapotranspiration flux curve in traditional groundwater models is replaced with a set of ecophysiologically based curves, one for each plant functional group present. For each group, the curve simulates transpiration declines that occur both as water levels decline below rooting depths and as waters rise to levels that produce anoxic soil conditions. Accuracy is further improved by more effective spatial handling of vegetation distribution, which allows modeling of surface elevation and depth to water for multiple vegetation types within each large model cell. The use of RIP-ET in groundwater models can improve the accuracy of basin scale estimates of riparian evapotranspiration rates, riparian vegetation water requirements, and water budgets. Two case studies are used to demonstrate that RIP-ET produces significantly different evapotranspiration estimates than the traditional method. When combined with vegetation mapping and a supporting program (RIP-GIS), RIP-ET also enables predictions of riparian vegetation response to water use and development scenarios. The RIP-GIS program links the head distribution from MODFLOW with surface digital elevation models, producing moderate- to high-resolution depth-to-groundwater maps. Together with information on plant rooting depths, these can be used to predict vegetation response to water allocation decisions. The different evapotranspiration outcomes produced by traditional and RIP-ET approaches affect resulting interpretations of hydro-vegetation dynamics, including the effects of groundwater pumping stress on existing habitats, and thus affect subsequent policy decisions. © 2005 Springer Science+Business Media, Inc.
- Steinitz, C., Faris, R., Flaxman, M., Vargas-Moreno, J. C., Canfield, T., Arizpe, O., Angeles, M., Cariño, M., Santiago, F., III, T. M., Lambert, C. D., Baird, K., & Godínez, L. (2005). A sustainable path? Deciding the future of La Paz. Environment, 47(6), 24-38.More infoAbstract: As the population soars in Mexico's scenic La Paz, decisionmakers are faced with the question of how best to manage development while protecting the area's environmental resources and aesthetics. An examination of 10 alternative futures helped show the possible impacts of their choices.
- Goodrich, D. C., Chehbouni, A., Goff, B., MacNish, B., Maddock, T., Moran, S., Shuttleworth, W. J., Williams, D. G., Watts, C., Hipps, L. H., Cooper, D. I., Schieldge, J., Kerr, Y. H., Arias, H., Kirkland, M., Carlos, R., Cayrol, P., Kepner, W., Jones, B., , Avissar, R., et al. (2000). Preface paper to the Semi-Arid Land-Surface-Atmosphere (SALSA) Program special issue. Agricultural and Forest Meteorology, 105(1-3), 3-20.More infoAbstract: The Semi-Arid Land-Surface-Atmosphere Program (SALSA) is a multi-agency, multi-national research effort that seeks to evaluate the consequences of natural and human-induced environmental change in semi-arid regions. The ultimate goal of SALSA is to advance scientific understanding of the semi-arid portion of the hydrosphere-biosphere interface in order to provide reliable information for environmental decision making. SALSA approaches this goal through a program of long-term, integrated observations, process research, modeling, assessment, and information management that is sustained by cooperation among scientists and information users. In this preface to the SALSA special issue, general program background information and the critical nature of semi-arid regions is presented. A brief description of the Upper San Pedro River Basin, the initial location for focused SALSA research follows. Several overarching research objectives under which much of the interdisciplinary research contained in the special issue was undertaken are discussed. Principal methods, primary research sites and data collection used by numerous investigators during 1997-1999 are then presented. Scientists from about 20 US, five European (four French and one Dutch), and three Mexican agencies and institutions have collaborated closely to make the research leading to this special issue a reality. The SALSA Program has served as a model of interagency cooperation by breaking new ground in the approach to large scale interdisciplinary science with relatively limited resources.
- Goodrich, D. C., Scott, R., Qi, J., Goff, B., Unkrich, C. L., Moran, M. S., Williams, D., Schaeffer, S., Snyder, K., MacNish, R., Maddock, T., Pool, D., Chehbouni, A., Cooper, D. I., Eichinger, W. E., Shuttleworth, W. J., Kerr, Y., Marsett, R., & Ni, W. (2000). Seasonal estimates of riparian evapotranspiration using remote and in situ measurements. Agricultural and Forest Meteorology, 105(1-3), 281-309.More infoAbstract: In many semi-arid basins during extended periods when surface snowmelt or storm runoff is absent, groundwater constitutes the primary water source for human habitation, agriculture and riparian ecosystems. Utilizing regional groundwater models in the management of these water resources requires accurate estimates of basin boundary conditions. A critical groundwater boundary condition that is closely coupled to atmospheric processes and is typically known with little certainty is seasonal riparian evapotranspiration ET). This quantity can often be a significant factor in the basin water balance in semi-arid regions yet is very difficult to estimate over a large area. Better understanding and quantification of seasonal, large-area riparian ET is a primary objective of the Semi-Arid Land-Surface-Atmosphere (SALSA) Program. To address this objective, a series of interdisciplinary experimental Campaigns were conducted in 1997 in the San Pedro Basin in southeastern Arizona. The riparian system in this basin is primarily made up of three vegetation communities: mesquite (Prosopis velutina), sacaton grasses (Sporobolus wrightii), and a cottonwood (Populus fremontii)/willow (Salix goodingii) forest gallery. Micrometeorological measurement techniques were used to estimate ET from the mesquite and grasses. These techniques could not be utilized to estimate fluxes from the cottonwood/willow (C/W) forest gallery due to the height (20-30 m) and non-uniform linear nature of the forest gallery. Short-term (2-4 days) sap flux measurements were made to estimate canopy transpiration over several periods of the riparian growing season. Simultaneous remote sensing measurements were used to spatially extrapolate tree and stand measurements. Scaled C/W stand level sap flux estimates were utilized to calibrate a Penman-Monteith model to enable temporal extrapolation between Synoptic measurement periods. With this model and set of measurements, seasonal riparian vegetation water use estimates for the riparian corridor were obtained. To validate these models, a 90-day pre-monsoon water balance over a 10 km section of the river was carried out. All components of the water balance, including riparian ET, were independently estimated. The closure of the water balance was roughly 5% of total inflows. The ET models were then used to provide riparian ET estimates over the entire corridor for the growing season. These estimates were approximately 14% less than those obtained from the most recent groundwater model of the basin for a comparable river reach.
- Nish, R. M., Unkrich, C. L., Smythe, E., Goodrich, D. C., & III, T. M. (2000). Comparison of riparian evapotranspiration estimates based on a water balance approach and sap flow measurements. Agricultural and Forest Meteorology, 105(1-3), 271-279.More infoAbstract: Estimates of evapotranspiration (ET) from riparian vegetation along a 122m reach of the San Pedro River using both a water balance approach and by scaling up sap flow measurements are compared. A sensitivity analysis was performed on the components of the water balance to assess the effects of measurement errors on estimates of ET using this method. It was concluded that by reducing the error in three key components to less than 5%, riparian ET could be estimated to an accuracy of 20-25% using the water balance method. The analysis also indicated that random measurement errors up to 10% in the water balance measurements would explain the difference between the water balance and sap flow ET estimates. Demonstrating agreement given reasonable error bounds provides confidence in the accuracy of both methods. (C) 2000 Elsevier Science B.V.
- Scott, R. L., Shuttleworth, W. J., Goodrich, D. C., & III, T. M. (2000). The water use of two dominant vegetation communities in a semiarid riparian ecosystem. Agricultural and Forest Meteorology, 105(1-3), 241-256.More infoAbstract: Consumptive water use from riparian evapotranspiration is a large component of many semiarid basins' groundwater budgets - comparable in magnitude to mountain front recharge and surface water discharge. In most long-term groundwater studies the amount of water used by phreatophytes is estimated by empirical formulae and extrapolation of measurements taken elsewhere. These approaches are problematic due to the uncertainties regarding the vegetation's water source (e.g., groundwater or recent precipitation) and its magnitude. Using micrometeorological techniques in this study, surface energy and water fluxes were measured for an annual cycle over two dominant types of vegetation in the riparian floodplain of the San Pedro River in southeastern Arizona. The vegetation communities were a perennial, floodplain sacaton grassland (Sporobolus wrightii) and a tree/shrub grouping composed largely of mesquite (Prosopis velutina). These measurements are compared with estimates from previous studies. Additionally, measurements of soil water content and water table levels are used to infer the dominant sources of the evaporated water. The results indicate that the grassland relied primarily on recent precipitation, while the mesquite obtained water from deeper in the soil profile. Neither appears to be strongly phreatophytic, which suggests that the dominant, natural groundwater withdrawals in the Upper San Pedro Basin are mainly confined to the narrow cottonwood/willow gallery that lines the river. (C) 2000 ElSevier Science B.V.
- III, M. T., & Vionnet, L. B. (1998). Groundwater capture processes under a seasonal variation in natural recharge and discharge. Hydrogeology Journal, 6(1), 24-32.More infoAbstract: "Capture" is the increase in recharge and the decrease in discharge that occurs when pumping is imposed on an aquifer system that was in a previous state of approximate dynamic equilibrium. Regional groundwater models are usually used to calculate capture in a two-step procedure. A steady-state solution provides an initial-head configuration, a set of flows through the boundaries for the modeled region, and the initial basis for the capture calculation. The transient solutions provide the total change in flows through the boundaries. A difference between the transient and steady-state solutions renders the capture calculation. When seasonality is a modeling issue, the use of a single initial hydraulic head and a single set of boundary flows leads to miscalculations of capture. Instead, an initial condition for each season should be used. This approach may be accomplished by determining steady oscillatory solutions, which vary through the seasons but repeat from year to year. A regional groundwater model previously developed for a portion of the San Pedro River basin, Arizona, USA, is modified to illustrate the effect that different initial conditions have on transient solutions and on capture calculations.
- Leenhouts, J. M., Bassett, R. L., & III, T. M. (1998). Utilization of intrinsic boron isotopes as Co-migrating tracers for identifying potential nitrate contamination sources. Ground Water, 36(2), 240-250.More infoAbstract: The stable isotopes of the conservative element boron,11B and 10B, have been employed as co-migrating isotopic tracers to trace potential sources of nitrate observed in ground water pumped from a large capacity 0.167 m3/s irrigation well in the Avra Valley of southeastern Arizona. The isotopic ratios provided an identifying signature for two nitrogen carrying source waters: municipal waste water and agricultural return flow. Additional chemical parameters were also examined to corroborate the isotopic indications. Boron isotopes provided a superior delineation of mixing processes in the system compared to the general inorganic chemical parameters. Findings of this investigation indicate that the water pumped by the study well at the beginning of the 1993 irrigation season was composed of a mixture of approximately 25% municipal waste water and 75% background ground water. As the irrigation season progressed, an increasing proportion of water was contributed by irrigation return flow from neighboring agricultural fields.
- Bouwer, H., & III, M. T. (1997). Making sense of the interactions between groundwater and streamflow: lessons for water masters and adjudicators. Rivers, 6(1), 19-31.More infoAbstract: The effects of groundwater pumping on streamflow are hydrologic issues that often are poorly understood in law. In some states, as illustrated with an Arizona example, different laws govern surface-and groundwater. In reality, however, surface-and groundwater form one continuum and conflicts can arise when different parties use both. How groundwater pumping affects streams depends on the depth to groundwater and whether or not the stream bottom is covered with fine sediment or organic deposits that control seepage. Using the hydrologic concept of capture, we present the basis quantitative aspects of stream-aquifer interactions in four case examples. More quantitative refinements and regional aspects can be achieved with computer models that can closely simulate specific regional or basin-wide systems. Once the broader concepts are sufficiently understood, integrated water management schemes can be developed that best resolve conflicts between the users of surface-and groundwater while protecting third parties, such as public and environmental interests. An underlying principle of these schemes should be the balance between the deisre for good scientific results and the economic reality of securing such results. We recommend steps to achieve the balance.
- Lacher, L. J., III, T. M., & Yeh, T. J. (1997). Inexpensive access tube installation of tensiometers below a flowing stream. Ground Water Monitoring and Remediation, 17(3), 76-77.
- Shafike, N., Duckstein, L., & Maddock, T. (1992). Multicriterion analysis of groundwater contamination management. Water Resources Bulletin, 28(1), 33-43.More infoAbstract: Multicriterion decision making (MCDM) techniques were used to analyze a groundwater contamination management problem from the viewpoint of conflicting multiple objectives. The groundwater management model was used to find a compromise strategy for trading off fresh water supply, containment of the waste, and total pumping cost in a hypothetical confined aquifer affected by previous waste disposal action. A groundwater flow model was used to formulate the hydraulic constraints. A linear system model was used to describe drawdown and velocity as functions of the decision variables which were pumping rates. The model determines the pumping location and rates. A modified ε-constraint method was used to generate the set of nondominated solutions which were the alternative compromise strategies. Three different MCDM techniques, Compromise programming (CP), ELECTRA II and MCQA II, were used to select a ``satisficing'' alternative. Analysis of the results showed that, although these techniques follow different principles, the same preferred strategies were reached. Also, it was noticed that maintaining high groundwater velocities is expensive and difficult. In order to meet a two year target date, large amounts of water had to be pumped. Therefore, rapid restoration results in large pumping volumes and high costs.
- III, T. M., & Lacher, L. J. (1991). Drawdown, velocity, storage, and capture response functions for multiaquifer systems. Water Resources Research, 27(11), 2885-2898.More infoAbstract: Capture describes the pumping-induced quantity of water gained by the aquifer from internal or boundary sources. Internal sources include rivers and hydraulically connected aquifers. Boundary sources include constant head and head-dependent boundaries. Although response functions are defined only for linear systems, a methodology is demonstrated for implementing response functions in cases of nonlinear capture. The value of response functions lies in their utility as hydrologic constraints in management optimization models. An example demonstrates the use of separable programming to determine the nonlinear effects of drawdown below the bottom of a streambed. -from Authors
- Shaukat, N., Heidari, M., & Maddock, T. (1987). EVALUATION OF SURFACE-WATER - GROUND-WATER INTERACTION COEFFICIENTS IN WATER-RESOURCES PLANNING MODEL.. Array, 264-269.More infoAbstract: A water-resources planning model formulated as a mixed-integer program is used to screen and sequence proposed projects such that the present cost of meeting future water demands is minimized. Surface-water - ground-water interactions are represented in the model by a set of constraints guaranteeing minimum surface-water flow which can be affected by diversions and well-field pumping. When well fields in a planning region are hydraulically connected to streams, consideration must be given to the impact of ground-water pumping on surface-water flows. The streamflow-requirement constraint in the planning model contains surface-water - ground-water interaction coefficients, which relate the quantity of water withdrawn from the stream to the quantity of water pumped by the well fields.
- Colarullo, S. J., Heidari, M., & III, T. M. (1984). Identification of an optimal groundwater management strategy in a contaminated aquifer. Water Resources Bulletin, 20(5), 747-760.
- III, T. M., Mercer, J. W., & Faust, C. R. (1982). Management model for power production from a geothermal field - 1: hot water reservoir and power plant model.. Water Resources Research, 18(3), 499-512.More infoAbstract: A management model is developed that determines the optimum economic recoverability of a hot-water geothermal reservoir undergoing exploitation for electric power generation. Integrates a physical model of the reservoir that predicts the areas of pressure decline due to withdrawals, and pressure rise due to reinjection of spent fluid, with a model of a two-stage steam turbine power plant that determines the quantity of electricity generated for a rate of hot-water extraction. Capital-, variable- and annual fixed costs are obtained for development, extraction and reinjection, the transmission system, and the power plant. Revenues are determined for electrical power production. Application of the model to a simplified, yet realistic example demonstrates that the methodology developed can be used for analyzing the management of an integrated geothermal reservoir power plant system.-from Authors
- III, T. M. (1981). An evaluation of the effectiveness of combining economic and physical ground-water models.. Array.More infoAbstract: Techniques for combining or coupling regional ground-water flow models with economic models are evaluated. The two principal techniques described are linking and embedding.-from US Govt Reports Announcements, 21, 1982
- Chiang, S. H., Wozniak, E., & III, T. M. (1978). WATER USAGE IN AN INTEGRATED COAL GASIFICATION PLANT.. Coal Process Technol, 4, 172-176.More infoAbstract: This study presents an attempt to provide a plant-level analysis that identified the key factors affecting rates of water consumption for the ″Synthane″ coal gasification process. The major factors included in the analysis are the coal composition and the Synthane process alternatives for waste treatment, gas purification and cooling water. Theoretical bases are developed to determine the limits for rates of process water and cooling water consumption. These limits are compared with rates of process water and cooling water consumption determined by a detailed material-energy balance for a hypothetical Synthane plant.
- Freeze, R. A., Gelhar, L. W., & III, T. M. (1978). Geostatistical concepts and stochastic methods in hydrogeology. Geology, 6(5), 297-298.
- Maddock Jr, T. (1978). River channel behaviour.. Water Spectrum, 10(2), 37-45.More infoAbstract: Man has lived beside streams flowing in their own alluvia since time immemorial and his efforts to control the constant variations in the stream channels are equally ancient. Yet even today these attempts by man, to a considerable extent, are a no-win game. -C.Keegan
- Chiang, S. H., Wozniak, E., & III, T. M. (1977). ANALYSIS OF WATER USAGE FOR AN INTEGRATED COAL GASIFICATION PLANT.. Array, 2, 1058-1062.More infoAbstract: A detailed plant-level evaluation of the rates of water consumption has been performed for five United States coals which are being considered as possible feedstocks for coal gasification processes. The consumptive rates of process water, cooling water and boiler water for a 250 million-SCFD SYNTHANE plant and its auxiliary facilities are estimated by a computerized material-energy balance. Theoretical bases are developed to determine the limits for rates of process water and cooling water consumption. The variation in the rates of water consumption due to coal composition and SYNTHANE process alternative are discussed.
- III, T. M. (1976). DRAWDOWN PREDICTION MODEL BASED ON REGRESSION ANALYSIS.. Water Resources Research, 12(4), 818-822.More infoAbstract: A technique for determining algebraic technological functions (ATF) relating the drawdown at wells to the quantity of water withdrawn from those wells is developed. The technique does not rely on the development of an analog or digital groundwater model to calculate the ATF's nor does it rely on a determination of distributions of transmissivity and storage coefficient. The inputs are the time series of historical pumping and water levels, the distances between wells, the radius of the well, and the duration of a pumping period. A stepwise regression analysis is used to determine the coefficients of the ATF. The functional form of the regression equation is based on standard results from groundwater analysis.
- Maddock Jr., T. (1976). EQUATIONS FOR RESISTANCE TO FLOW AND SEDIMENT TRANSPORT IN ALLUVIAL CHANNELS.. Water Resources Research, 12(1), 11-21.More infoAbstract: The commonly accepted parameters for sediment transport and resistance to flow of alluvial channels are evaluated and found to be inadequate. A resistance equation and a sediment transport equation are proposed for alluvial channels. Presently used equations are shown to be approximations of combinations of these two equations. The two equations describe channel behavior and sediment transport better than other equations, and they are shown to be particularly effective in describing the effects of changes of temperature on water discharge.
- III, T. M., & Haimes, Y. Y. (1975). TAX SYSTEM FOR GROUNDWATER MANAGEMENT.. Water Resources Research, 11(1), 7-14.More infoAbstract: A tax scheme is developed that will create an incentive among users to conserve groundwater and reduce the external diseconomies that pumping produces. Quotas are established for wells by using an agricultural management model. If a user pumps more than the quota established for his well, he may be assessed a tax; if a user pumps less than his quota, he may be entitled to a rebate. However, taxes are collected and redistributed in such a way that zero taxes are accumulated from year to year.
- III, T. M. (1974). NONLINEAR TECHNOLOGICAL FUNCTIONS FOR AQUIFERS WHOSE TRANSMISSIVITIES VARY WITH DRAWDOWN.. Water Resources Research, 10(4), 877-881.More infoAbstract: An algebraic technological function (ATF) is shown to exist for an aquifer whose flow to wells can be remodeled by Boussinesq's equation. Drawdown is shown to be an infinite power series in pumping values, and the ATF is provided by a finite sum of the power series. The number of terms necessary for the finite sum to provide a good approximation to the infinite series is shown to depend on a ratio of drawdown to saturated thickness. The ATF can be used in optimization techniques or as a method for predicting drawdowns from pumping.
- III, T. M. (1974). OPERATION OF A STREAM-AQUIFER SYSTEM UNDER STOCHASTIC DEMANDS.. Water Resources Research, 10(1), 1-10.More infoAbstract: It is possible to develop operating rules for the conjunctive use of surface water and groundwater when the demand and supply sources are stochastic. These rules allow the quantities of water pumped from wells, diverted from streams, spread, and returned to the stream after use to be determined for a given time period even if the required needs and availability of supply are uncertain at the beginning of the time period. These rules are dependent on a technological function relating streamflow interaction with well pumping and with the statistics of the demands, streamflow, pumping and drawdowns.
- MADDOCK, T. (1974). NONLINEAR TECHNOLOGICAL FUNCTIONS FOR AQUIFERS WHOSE TRANSMISSIVITIES VARY WITH DRAWDOWN.. Water Resources Research, 10(4), AUGUST, 1974.More infoAbstract: AN ALGEBRAIC TECHNOLOGICAL FUNCTION (ATF) IS SHOWN TO EXIST FOR AN AQUIFER WHOSE FLOW TO WELLS CAN BE RE - MODELED BY BOUSSINESQ'S EQUATION.DRAWDOWN IS SHOWN TO BE AN INFINITE POWER SERIES IN PUMPING VALUES, AND THE ATF IS PROVIDED BY A FINITE SUM OF THE POWER SERIES.THE NUMBER OF TERMS NECESSARY FOR THE FINITE SUM TO PROVIDE A GOOD APPROXIMATION TO THE INFINITE SERIES IS SHOWN TO DEPEND ON A RATIO OF DRAWDOWN TO SATURATED THICKNESS.THE ATF CAN BE USED IN OPTIMIZATION TECHNIQUES OR AS A METHOD FOR PREDICTING DRAWDOWNS FROM PUMPING.(A).
- MADDOCK, T. (1974). THE OPERATION OF A STREAM-AQUIFER SYSTEM UNDER STOCHASTIC DEMANDS.. Water Resources Research, 10(1), FEBRUARY, 1974.More infoAbstract: IT IS POSSIBLE TO DEVELOP OPERATING RULES FOR THE CONJUNCTIVE USE OF SURFACE WATER AND GROUNDWATER WHEN THE DEMAND AND SUPPLY SOURCES ARE STOCHASTIC.THESE RULES ALLOW THE QUANTITIES OF WATER PUMPED FROM WELLS, DIVERTED FROM STREAMS, SPREAD, AND RETURNED TO THE STREAM AFTER USE TO BE DETERMINED FOR A GIVEN PERIOD EVEN IF THE REQUIRED NEEDS AND AVAILABILITY OF SUPPLY ARE UNCERTAIN AT THE BEGINNING OF THE TIME PERIOD.THESE RULES ARE DEPENDENT ON A TECHNOLOGICAL FUNCTION RELATING STREAMFLOW INTERACTION WITH WELL PUMPING AND WITH THE STATISTICS OF THE DEMANDS, STREAMFLOW, PUMPING, AND DRAWDOWNS.(A)
- MADDOCK, T. (1973). A ROLE OF SEDIMENT TRANSPORT IN ALLUVIAL CHANNELS.. J. HYDRAUL. DIV., ASCE, 99 , HY11, NOVEMBER, 1973.More infoAbstract: ONCE A CRITICAL AMOUNT OF SEDIMENT IS BEING MOVED IN AN ALLUVIAL CHANNEL, VELOCITY CAN BE EXPRESSED AS A FUNCTION OF SLOPE AND OF SIZE AND COMPOSITION OF THE MOVING SEDIMENT LOAD.DEPTH IS A REDUNDANT PARAMETER.AT SEDIMENT TRANSPORT RATES BELOW CRITICAL, DEPTH IS AN EFFECTIVE PARAMETER.METHODS OF DETERMINING THE SIZE AND COMPOSITION OF THE MOVING SEDIMENT LOAD ARE ANALYSED AS IS THE PROBLEM OF DETERMINING WHEN DEPTH BECOMES REDUNDANT.THE PHENOMENA OF FILL AND SCOUR AT ALLUVIAL CHANNEL SECTIONS IS ALSO CONSIDERED.(A)
- Maddock Jr., T. (1973). ROLE OF SEDIMENT TRANSPORT IN ALLUVIAL CHANNELS.. ASCE J Hydraul Div, 99(HY11), 1915-1931.More infoAbstract: Methods of determining the size and composition of the moving sediment load are analyzed as is the problem of determining when depth becomes redundant. The phenomena of fill and scour at alluvial channel sections is also considered.
- Crosby, D. S., & III, T. M. (1970). Estimating coefficients of a flow generator for monotone samples of data. Water Resources Research, 6(4), 1079-1086.More infoAbstract: If a set of flow records continuous in collection to the present has different starting times, it forms a monotone sample. The monotone sample may yield an inconsistent lag zero covariance matrix. In addition, it may be impossible to calculate real-value coefficients for a flow generator, leading to some complex values for the synthetic flow trace. A technique is presented that produces a consistent lag zero covariance matrix and a real-value multisite streamflow generator.
- III, T. M., & Crosby, B. S. (1970). Estimating expected values for monotone samples. Water Resources Research, 6(6), 1743-1745.More infoAbstract: New expected value estimates for monotone sample data can be produced while using the technique to produce a consistent covariance matrix.
- MADDOCK, T., & JR, . (1969). BEHAVIOR OF STRAIGHT OPEN CHANNELS WITH MOVABLE BEDS. US Geological Survey Professional Paper.More infoAbstract: The chief variables related to the behavior of alluvial channels are mean velocity, depth, width, slope, quantity of sediment transport, and sediment size composition. Relation between sediment load and velocity, two-, and three-dimensional flow are analyzed.