• Analysis of hydrologic data collected by the U.S. Bureau of Land Management 1987-1995 and recommendations for future monitoring programs

      Sharma, Vandana; Mac Nish, Robert D.; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona; Arizona Research Laboratory for Riparian Studies (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1997)
      The purpose of this study was to establish a more efficient monitoring program for the San Pedro Riparian National Conservation Area (SPRNCA). This report analyzes data on stream flow measurements taken at nine locations on the San Pedro river and one location on the Babocomari river and ground water levels in eighteen wells collected by the BLM over the period from 1987 to 1995 and discusses possible causes for trends and anomalies in the data. The report also recommends future data collection and analytical efforts. All of the stream discharge data and some of the groundwater levels were collected at discrete and unsystematic intervals, and further, the streamflow measurements may not have been collected at the same location at each site. Surface water flow was measured by a Marsh- McBirney flow meter.
    • An analysis of the effects of retiring irrigation pumpage in the San Pedro riparian national conservation area, Cochise county, Arizona

      Sharma, Vandana; Nish, Robert D. Mac; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona; Arizona Research Laboratory for Riparian Studies (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2000)
      A seasonal groundwater model was developed to simulate fluxes and head distributions with periodic boundary conditions within the San Pedro Riparian National Conservation Area (SPRNCA) in southeastern Arizona. This model incorporated a seasonal approach for the period 1940-1995. Two years were used to simulate streamflow, 1990 and 1995. The model, as currently calibrated, does not accurately reproduce observed baseflow conditions in the San Pedro River and simulates an exaggerated effect of retiring irrigation within the SPRNCA. The model simulated increased baseflows while the observed baseflows declined at the USGS Charleston stream gage, though increases in baseflow contributions between Hereford Bridge and Lewis Springs have been reported. The original (Corell, et al., 1996) model and the seasonal transient model suffer from over- estimation of discharge from the floodplain aquifer to the San Pedro river, as well as errors in the seasonal transient model's simulation of riparian ET, and seasonal variations in stream conductance. These problems precluded the seasonal transient model from replicating the observed baseflows in the San Pedro river at the Charleston bridge, however, the results of the simulation are thought to be qualitatively indicative of changes in the flow system resulting from the retirement of irrigated agriculture in the San Pedro Riparian National Conservation Area. Possible sources for this problem include replacement of irrigation stresses by the expansion of cones of depression more distant from the river, overestimation of mountain front recharge, poor baseflow estimates and evapotransipration calculations from the stream gages at Charleston and Palominas, and the effects of a recently discovered silt -clay body that may dampen the speed of the rivers response to changes in stress. Additional efforts to re- calibrate the model, taking these areas into account, should provide better simulated baseflow values of the observed data.
    • APPLICATION OF BORON ISOTOPE RATIOS FOR IDENTIFYING NITRATE CONTAMINATION SOURCES IN THE GROUNDWATER OF AVRA VALLEY, ARIZONA

      Leenhouts, James Merrell; Basset, R. L.; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1994-06)
      The stable isotopes of the conservative element boron, 11B and 1°B, have been employed as co- migrating isotopic tracers to determine the origin of nitrate observed in groundwater from a large capacity (2500 gpm) irrigation well in the Avra Valley of southeastern Arizona. The isotopic ratios of the conservative element, boron, provided an identifying signature for various nitrate rich source waters. Additional chemical parameters were also examined to corroborate the isotopic indications. Findings of this investigation indicate that most of the nitrate observed in groundwater from well CMID 18 at the beginning of the 1993 irrigation season was due to municipal wastewater contamination. As the irrigation season progressed, an increasing proportion of nitrate was contributed by irrigation return flow from neighboring agricultural fields.
    • CONFUSION WHERE GROUND AND SURFACE WATERS MEET: GILA RIVER GENERAL ADJUDICATION, ARIZONA AND THE SEARCH FOR SUBFLOW

      Sobczak, Robert V.; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1994-10)
      Arizona is presently in the midst of a general adjudication for the Gila River system -- the watershed which comprises the southern two- thirds of the state. The purpose of the adjudication is to prioritize all water claims in the river system: both state -established and federally reserved rights. Arizona adheres to a bifurcated (or divided) system of water law which only recognizes a component of ground water -- called subflow -- to be appropriable. Wells which pump non-appropriable water -- called tributary flow -- are not to be included in the adjudication. The problem is that federal laws do not recognize this artificial bifurcation. The challenge lies in identifying a subflow zone which satisfies the hydrologic fiction of existing state precedents and the hydrologic reality of federal statutes. At the core of the problem lies the fate of Arizona's perennial stream water and the fulfillment of federally reserved tribal water rights. Thus, larger questions loom: can Arizona law reconcile its glutinous past with a water -scarce future, will the adjudication ever reach a finality, and even if it does, will it be a finality that all sides can live with?
    • Effluent recharge to the Upper Santa Cruz River floodplain aquifer, Santa Cruz county, Arizona

      Scott, Paul S.; Mac Nish, Robert D.; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona; Arizona Research Laboratory for Riparian Studies (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1997)
      The City of Nogales, Arizona, is in the Santa Cruz Active Management Area and is subject to the assured water supply and conservation mandates of the 1980, Groundwater Management Act (State of Arizona, 1980). The primary water supply for both Nogales Arizona, and Nogales, Sonora, (commonly referred to as Ambos Nogales) is groundwater pumped from the shallow alluvial aquifers which underlie the Upper Santa Cruz River in Arizona and Mexico, and its tributaries (principally Nogales Wash and Potrero Creek). Nogales, Sonora also obtains water from the Los Alisos Basin, which is south of the Santa Cruz Basin in Mexico (Carruth, 1995). The NIWTP provides wastewater treatment for Ambos Nogales, and discharges treated wastewater to the Upper Santa Cruz River near the confluence with Nogales Wash and Sonoita Creek. The discharge of effluent creates an intermittent stream from the NIWTP outfall for approximately 13 river miles to Tubac, Arizona. The conservation mandates of the 1980, Groundwater Management Act (State of Arizona, 1980) require the City of Nogales, Arizona to prove the existence of a 100-year water supply as a condition for future growth. The Act also allows Nogales, Arizona to receive recharge credits for the portion of effluent that recharges the aquifer underlying the Santa Cruz River. The recharge credits will be used by the City of Nogales as partial proof of a 100-year water supply (Carruth, 1995).
    • Flow model for the Bingham cienega area, San Pedro river basin, Arizona: a management and restoration tool

      Ronayne, Michael James; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1996-10)
      A finite element groundwater flow model was used to support a hydrologic assessment for a study area in the Lower San Pedro River Basin which contains the Bingham Cienega. Consolidated sedimentary rocks associated with an extension of the Catalina Core Complex truncate the floodplain aquifer system in the study area. The elevated water table produced by this "hardrock" results in spring discharge at the cienega and a locally gaining reach of the San Pedro River. The steady -state model suggests that recharge (and discharge) components for the floodplain aquifer sum to 3.10 cfs. Mountain front recharge, underflow, and stream leakage are the primary recharge mechanisms, while stream leakage, evapotranspiration, spring flow, and underflow out are sources for groundwater discharge. A steady -oscillatory model was used to account for seasonal periodicity in the system's boundary conditions. Monthly variation in the evapotranspiration rate was offset primarily by storage changes in the aquifer. Due to a lack of measured hydrologic data within the study area, results from the model simulations are only preliminary. Model development and the subsequent sensitivity analyses have provided insight into what type of data needs to be collected. Head measurements are most needed in the area just downstream from Bingham Cienega. The mountain front recharge and evapotranspiration rates are shown to be highly sensitive parameters in the model; improved estimation of these values would be helpful. Spring discharge would be a valuable calibration tool if it could be accurately measured. A more extensive record of stream baseflow in the San Pedro River should be established. After more hydrologic data is collected, the model could be recalibrated so as to better represent the system. Eventually, this tool may be used in direct support of management and/or restoration decisions.
    • Ground-water flow and interaction with surface water in San Bernardino valley, Cochise county, Arizona and Sonora, Mexico

      Davis, Laura Agnes; Maddock, Thomas, III; Nish, Robert Mac; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1997-01)
      In the center of San Bernardino Valley in southeastern Arizona, San Bernardino National Wildlife Refuge provides unique wetlands habitat for endangered fish and wildlife. Confined conditions exist within the refuge, producing springs, artesian wells, and perennial pools along Black Draw, the main surface-water drainage. A numerical flow model was constructed in order to understand the hydrogeologic system of the basin. Annual inflows to the basin include 50,171 acre-feet of mountain-front recharge, 4,360 acft of underflow, and 7,074 ac-ft of river leakage. Annual outflows consist of 57,704 ac-ft of underflow, 3,010 ac-ft of river leakage, 537 ac-ft of evapotranspiration, 346 ac-ft of spring discharge, and 5 ac-ft of stream leakage. Further investigations are needed to refine the annual steady-state model, develop a seasonal (oscillatory) model, and construct transient simulations predicting responses of the hydrologic system to climatic and/or anthropogenic stresses. Extremely large mountain-front recharge and subsurface outflow estimates should be improved by conducting pump tests, geophysical studies, and isotope dating and chemistry analyses of ground water, and by collecting more water levels in Sonora. These studies will also provide information on the role of basalt flows in mountain-front recharge distribution and ground-water flow patterns. The study concludes with a recommended monitoring program for the refuge.
    • Investigations of stream-aquifer interactions using a coupled surface-water and ground-water flow model

      Vionnet, Leticia Beatriz; Maddock, Thomas, III; Goodrich, David C.; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1997-01)
      A finite element numerical model is developed for the modeling of coupled surface-water flow and ground-water flow. The mathematical treatment of subsurface flows follows the confined aquifer theory or the classical Dupuit approximation for unconfined aquifers whereas surface-water flows are treated with the kinematic wave approximation for open channel flow. A detailed discussion of the standard approaches to represent the coupling term is provided. In this work, a mathematical expression similar to Ohm's law is used to simulate the interacting term between the two major hydrological components. Contrary to the standard approach, the coupling term is incorporated through a boundary flux integral that arises naturally in the weak form of the governing equations rather than through a source term. It is found that in some cases, a branch cut needs to be introduced along the internal boundary representing the stream in order to define a simply connected domain, which is an essential requirement in the derivation of the weak form of the ground-water flow equation. The fast time scale characteristic of surface-water flows and the slow time scale characteristic of ground-water flows are clearly established, leading to the definition of three dimensionless parameters, namely, a Peclet number that inherits the disparity between both time scales, a flow number that relates the pumping rate and the streamflow, and a Biot number that relates the conductance at the river-aquifer interface to the aquifer conductance. The model, implemented in the Bill Williams River Basin, reproduces the observed streamflow patterns and the ground-water flow patterns. Fairly good results are obtained using multiple time steps in the simulation process.
    • A lower San Pedro river basin groundwater flow model

      Whittier, Jonathan Douglas; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2004)
      Water issues in the Lower San Pedro River basin in southeastern Arizona are becoming increasingly contentious as urban development, agriculture, and mining needs compete with the needs of the riparian habitat. To better understand the water demands in this basin, a new groundwater flow model has been created. First, the conceptual model was produced using various Geographic Information System (GIS) applications. A new method allocating digital precipitation data to the smaller drainages within the watershed was used to estimate mountain front recharge. Well data was gathered from both the United States Geological Survey (USGS) and Arizona Department of Water Resources (ADWR). Depth to bedrock was interpolated from an earlier gravity survey of the area. The current extent of riparian vegetation was determined by recent United States Forest Service aerial photography. GIS shapefiles were created depicting the data necessary for MODFLOW. Second, the numerical MODFLOW model was formed using GMS (Groundwater Modeling System), a graphical user interface for MODFLOW. GMS was used to create the grid, allocate the information from the shapefiles into MODFLOW input files, create the MODFLOW numerical model, and calibrate the model. The model results project potential impacts to the overall sustainability of groundwater within the basin. 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 along the San Pedro River.
    • Management Model for Electrical Power Production from a Hot-Water Geothermal Reservoir

      Maddock, Thomas, III; Mercer, James W.; Faust, Charles R.; Attanasi, Emil D.; University of Arizona; U.S. Geological Survey (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1979-11)
      A management model is developed that determines the optimum economic recoverability of a particular hot -water geothermal reservoir undergoing exploitation for electric power generation. The management model 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 costs, variable costs and annual fixed costs are obtained for the reservoir development, extraction and reinjection, the transmission system, and the power plant. Revenues are determined for electrical power production. Application of the management model to a simplified, yet realistic example reservoir demonstrates that the methodology developed in this report can be used for analyzing the management of an integrated geothermal reservoir-power plant system.
    • Modeling of Ground-Water Flow and Surface/Ground-Water Interaction for the San Pedro River Basin Part I Mexican Border to Fairbank, Arizona

      Vionnet, Leticia Beatriz; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1992)
      Many hydrologic basins in the southwest have seen their perennial streamflows turn to ephemeral, their riparian communities disappear or be jeopardized, and their aquifers suffer from severe overdrafts. Under -management of ground -water exploitation and of conjunctive use of surface and ground waters are the main reasons for these events.
    • MODRSP: a program to calculate drawdown, velocity, storage and capture response functions for multi-aquifer systems

      Maddock, Thomas, III; Lacher, Laurel J.; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1991)
      MODRSP is program used for calculating drawdown, velocity, storage losses and capture response functions for multi - aquifer ground -water flow systems. Capture is defined as the sum of the increase in aquifer recharge and decrease in aquifer discharge as a result of an applied stress from pumping [Bredehoeft et al., 19821. The capture phenomena treated by MODRSP are stream- aquifer leakance, reduction of evapotranspiration losses, leakance from adjacent aquifers, flows to and from prescribed head boundaries and increases or decreases in natural recharge or discharge from head dependent boundaries. The response functions are independent of the magnitude of the stresses and are dependent on the type of partial differential equation, the boundary and initial conditions and the parameters thereof, and the spatial and temporal location of stresses. The aquifers modeled may have irregular -shaped areal boundaries and non -homogeneous transmissive and storage qualities. For regional aquifers, the stresses are generally pumpages from wells. The utility of response functions arises from their capacity to be embedded in management models. The management models consist of a mathematical expression of a criterion to measure preference, and sets of constraints which act to limit the preferred actions. The response functions are incorporated into constraints that couple the hydrologic system with the management system (Maddock, 1972). MODRSP is a modification of MODFLOW (McDonald and Harbaugh, 1984,1988). MODRSP uses many of the data input structures of MODFLOW, but there are major differences between the two programs. The differences are discussed in Chapters 4 and 5. An abbreviated theoretical development is presented in Chapter 2, a more complete theoretical development may be found in Maddock and Lacher (1991). The finite difference technique discussion presented in Chapter 3 is a synopsis of that covered more completely in McDonald and Harbaugh (1988). Subprogram organization is presented in Chapter 4 with the data requirements explained in Chapter 5. Chapter 6 contains three example applications of MODRSP.
    • MR2K: A program to calculate drawdown, velocity, storage and capture response functions

      Maddock, Thomas, III; Lacher, Laurel J.; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2008)
      A program, MR2K, used for calculating drawdown, velocity, storage loss, and capture response functions for multi -aquifer groundwater flow systems was developed. Capture is defined as the sum of the increase in aquifer recharge and decrease in aquifer discharge as a result of an applied stress from groundwater pumping. The capture phenomena treated are stream-aquifer leakance, reduction of evapotranspiration losses, reduction of drain flows, flows to and from prescribed head boundaries, and increases or decreases in natural recharge or discharge from head-dependent boundaries. The response functions are independent of the magnitude of the pumping stresses, and are dependent on the type of partial differential equation, boundary and initial conditions and the parameters thereof, and the spatial and temporal locations of stresses. The aquifers modeled may have irregular- shaped boundaries and nonhomogeneous transmissive and storage qualities. The stresses are groundwater withdrawals from wells. The utility of response functions arises from their capacity to be embedded in management models such as decision support systems. The response functions are incorporated into the objective function or constraints that couple the hydrologic system with the management system. Three response -function examples are presented for a hypothetic basin.
    • PRELIMINARY VEGETATION AND HYDROLOGIC ANALYSES FOR BINGHAM CIENEGA

      Baird, Kathryn J.; Ronayne, Michael J.; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1997-01)
      This report is in two parts. The first part covers the ecological processes pertinent to the restoration of Bingham Cienega. The second part presents a subregional groundwater flow model for analyzing the water budget, stream and spring behavior, and water table configuration. Because of the sparsity of ecological and hydrologic data, both parts must be considered as preliminary studies.
    • RESPONSE FUNCTIONS IN THE CRITICAL COMPARISON OF CONJUNCTIVE MANAGEMENT SYSTEMS IN TWO WESTERN STATES

      Lacher, Laurel Jane,1964-; Maddock, Thomas, III; Lord, William B.; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1993-04)
      Conjunctive management of surface and ground -water resources on state and local levels is a relatively new political phenomenon. This type of management has evolved, in part, in response to growing populations with ever -increasing, and often conflicting, water demands. In addition, a more sophisticated technical understanding of the physical link between groundwater and surface waters has led water managers to reconsider historical strategies for solving water supply problems. In light of growing demand and improved technology, some western states have begun the transition from crisis- oriented water management to one of long -term planning for population growth and environmental protection. This planning process requires that the constituents of a region define their water use goals and objectives so that various approaches to conjunctive management may be evaluated for their suitability to that particular physical and socio- political environment.
    • A riparian evapotranspiration package

      Maddock, Thomas, III; Baird, Kathryn J.; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2002-10)
      A new evapotranspiration package for the U.S. Geological Survey's groundwater -flow model, MODFLOW, is documented. The Riparian Evapotranspiration Package (RIP-ET), provides flexibility in simulating riparian and wetland evapotranspiration (ET) not provided by the MODFLOW-96 Evapotranspiration (EVT) Package, nor by the MODFLOW-2000 Segmented Function Evapotranspiration (ETS1) Package. This report describes how the package was conceptualized and provides input instructions, listings and explanations of the source code, and an example simulation. Traditional approaches to modeling ET processes assume a piecewise linear relationship between ET flux rate and hydraulic head. The Riparian ET Package replaces this traditional relationship with a segmented, nonlinear dimensionless curve that reflects the eco-physiology of riparian and wetland ecosystems. Evapotranspiration losses from these ecosystems are dependent not only on hydraulic head but on the plant types present. User-defined plant functional groups (PFGs) are used to elucidate the interactive processes of plant ET with groundwater conditions. Five generalized plant functional groups based on transpiration rates, plant rooting depth, and drought tolerance are presented: obligate wetland, shallow-rooted riparian, deep-rooted riparian, transitional riparian and bare ground/open water. Plant functional groups can be further divided into subgroups (PFSG) based on plant size and/or density. The Riparian ET Package allows for partial habitat coverage and mixtures of plant functional subgroups to be present in a single model cell. This requires a determination of fractional coverage for each of the plant functional subgroups present in a cell to simulate the mixture of coverage types and resulting ET. The fractional cover within a cell has three components: 1) fraction of active habitat, 2) fraction of plant functional subgroup in a cell, and 3) fraction of plant canopy area. The Riparian ET package determines the ET rate for each plant functional group in a cell, the total ET in the cell, and the total ET rate over the region of simulation.
    • A riparian evapotranspiration package for MODFLOW-2000 and MODFLOW-2005

      Maddock, Thomas, III; Baird, Kathryn J.; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2008-03)
      A new version of an evapotranspiration package for the U.S. Geological Survey's groundwater -flow model, MODFLOW, is documented. The Riparian Evapotranspiration Package (RIP-ET) provides flexibility in simulating riparian and wetland evapotranspiration (ET) not provided by the MODFLOW -2000 and MODFLOW 2005 traditional Evapotranspiration (EVT) Package, nor by the MODFLOW-2000 Segmented Function Evapotranspiration (ETS1) Package. This report describes how the package was conceptualized and provides input instructions, listings and explanations of the source code, and an example simulation. Traditional approaches to modeling ET processes assume a piecewise linear relationship between ET flux rate and hydraulic head. The RIP-ET replaces this traditional relationship with a segmented, nonlinear dimensionless curve that reflects the eco-physiology of riparian and wetland ecosystems. Evapotranspiration losses from these ecosystems are dependent not only on hydraulic head but on the plant types present. User -defined plant functional groups (PFGs) are used to elucidate the interactive processes of plant ET with groundwater conditions. Five generalized plant functional groups based on transpiration rates, plant rooting depth, and water tolerance ranges are presented: obligate wetland, shallow-rooted riparian, deep- rooted riparian, transitional riparian and bare ground /open water. Plant functional groups can be further divided into subgroups (PFSG) based on plant size, density or other user defined field. The RIP -ET allows for partial habitat coverage and mixtures of plant functional subgroups to be present in a single model cell. Habitat areas are designated by polygons. A polygon can contain a mixture of PFSGs and bare ground, and is assigned a calculated land surface elevation. This process requires a determination of fractional coverage for each of the plant functional subgroups present in a polygon to simulate the mixture of coverage types and resulting ET. The fractional cover within a cell has two components: 1) the polygonal fraction of active habitat in a cell, and 2) fraction of plant flux area in a polygon. The RIP -ET determines the ET rate for each plant functional group in a cell, the total ET in the cell, and the total ET rate over the region of simulation.
    • SIMULATION OF GROUND-WATER FLOW TO ASSESS THE EFFECTS OF PUMPING AND CANAL LINING ON THE HYDROLOGIC REGIME OF THE MESILLA BASIN: Dona Ana County, New Mexico & El Paso County, Texas

      Lang, Patrick T.; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1995-04)
      This study, which is to provide information to a settlement over the rights to water resources in the Mesilla Basin, uses a groundwater model to estimate how pumping in the basin affects the hydrologic regime.
    • Simulation of groundwater conditions in the Colorado River Delta, Mexico

      Feirstein, Eden Jael; Zamora, Francisco; Vionnet, Leticia Beatriz; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona; Sonoran Institute; Facultad de Ingeniería y Ciencias Hídricas (FICH) - Universidad Nacional del Litoral (UNL) (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2008-05)
      The Colorado River Delta (CRD) is a large sedimentary complex within a tectonically active structurally controlled basin. The CRD lies across the U.S.-Mexico international boundary and is traversed by the Colorado River on is way to the Gulf of California. Multidisciplinary research addressing the impact of the hydrologic change in the CRD has been increasing since the 1980's. To help expand the base of this knowledge, a groundwater model for the CRD within Mexico was developed. A conceptual model was constructed and transformed within the Department of Defense Groundwater Modeling Software (GMS) into a numerical model using the MODFLOW 2005 code made available by the U.S. Geological Survey. Model results indicates that large scale flood events on the Colorado River act as a recharge to the aquifer and show that the relationship between groundwater withdrawals and capture are evident on an seasonal scale. The model will form the parent basis for further Delta studies using the Local Grid Refinement (LRG), a methodology inherent to MODFLOW 2005.
    • Simulation of Groundwater Conditions in the Upper San Pedro Basin for the Evaluation of Alternative Futures

      Goode, Tomas Charles; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona; University of Arizona Research Laboratory for Riparian Studies (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2000)
      The creation of the groundwater model of the Upper San Pedro Basin included two developmental phases: the creation of a conceptual and numerical model. The creation of the conceptual model was accomplished through the utilization of Geographic Information System (GIS) software, namely ArcView, used primarily to view and create point, line, and polygonal shapes. The creation of a numerical model was accomplished by the infusion of the conceptual model into a 3D finite difference grid used in MODFLOW groundwater software from the U.S. Geological Survey. MODFLOW computes the hydraulic head (water level) for each cell within the grid. The infusion of the two models (conceptual and numerical) was allowed through the use of Department of Defense Groundwater Modeling System (GMS) software. The time period for groundwater modeling began with predevelopment conditions, or "steady state." Steady state conditions were assumed to exist in 1940. The steady state was used as the initial condition for the subsequent transient analysis. The transient simulation applied historical and current information of pumping stresses to the system from 1940 to 1997. After modeling current conditions, Alternative Futures' scenarios were simulated by modifying current stresses and by adding new ones. The possible future impacts of to the hydrologic system were then evaluated.