Field verification of stream-aquifer interactions: Colorado School of Mines survey field, Golden, Colorado

June 1993.Includes bibliographical references (pages 102-105).The nature of stream/aquifer interactions is determined in a field study on a stream at the Colorado School of Mines survey field in Golden, Colorado. The study measured the temporal and spatial variability during the spring and summer of 1992 of hydraulic parameters controlling stream/aquifer interactions at the streambed level of detail. Included is the determination of the shallow hydraulic gradient directly beneath the stream; measurement using established piesometers and an air permeameter; and, characterization of the streambed. The area was monitored during a variety of conditions. A number of conclusions are drawn regarding the nature of stream/aquifer interactions at the site. The duration of groundwater was found to depend on the amount of precipitation in the area. The response of the groundwater system to precipitation is on the order of days, while the responses to changes in stream stage is almost immediate. The shallow groundwater gradients calculated form the water level data indicates the presence of two groundwater discharge zones at the site. The total reach of stream is generally gaining water form the groundwater system. The range of stream flow velocities observed is fairly uniform and sufficient to transport unconsolidated sediments up to 2 mm in diameter. The grain size distribution was analyzed.Grant no. 14-08-0001-2008, Project no. 11; financed in part by the U.S. Dept. of the Interior, Geological Survey, through the Colorado Water Resources Research Institute

Field assessment of stream/aquifer interaction under semi-arid conditions and problems with computer representation

June 1994.Also listed online under Open file reports list as no. 6.Revision of Bissett's thesis (M. Eng.--Colorado School of Mines, 1994).Includes bibliographical references (pages 59-60).Financed in part by the U.S. Dept. of the Interior, Geological Survey

MMA, A Computer Code for Multi-Model Analysis

This report documents the Multi-Model Analysis (MMA) computer code. MMA can be used to evaluate results from alternative models of a single system using the same set of observations for all models. As long as the observations, the observation weighting, and system being represented are the same, the models can differ in nearly any way imaginable. For example, they may include different processes, different simulation software, different temporal definitions (for example, steady-state and transient models could be considered), and so on. The multiple models need to be calibrated by nonlinear regression. Calibration of the individual models needs to be completed before application of MMA. MMA can be used to rank models and calculate posterior model probabilities. These can be used to (1) determine the relative importance of the characteristics embodied in the alternative models, (2) calculate model-averaged parameter estimates and predictions, and (3) quantify the uncertainty of parameter estimates and predictions in a way that integrates the variations represented by the alternative models. There is a lack of consensus on what model analysis methods are best, so MMA provides four default methods. Two are based on Kullback-Leibler information, and use the AIC (Akaike Information Criterion) or AICc (second-order-bias-corrected AIC) model discrimination criteria. The other two default methods are the BIC (Bayesian Information Criterion) and the KIC (Kashyap Information Criterion) model discrimination criteria. Use of the KIC criterion is equivalent to using the maximum-likelihood Bayesian model averaging (MLBMA) method. AIC, AICc, and BIC can be derived from Frequentist or Bayesian arguments. The default methods based on Kullback-Leibler information have a number of theoretical advantages, including that they tend to favor more complicated models as more data become available than do the other methods, which makes sense in many situations

Development of characterization approaches and a management tool for the groundwater-surface water system in the vicinity of Sutherland Reservoir and Gerald Gentlemen Station Lincoln County, Nebraska

October 2009.Includes bibliographical references

Estimation of groundwater recharge using neutron probe moisture readings near Golden, Colorado

CWRRI Completion Report No. 165.November 16, 1992.To better understand recharge processes under natural conditions in the Denver Basin, a vadose zone monitoring study was conducted from September 1991 through September 1992 at a site near Golden, Colorado. Six access tubes were monitored with a neutron probe to a depth of 8.75 feet to determine moisture profiles several times a month. Moisture characteristic curves were developed for soil samples which were extracted during access tube installation. The van Genuchten function was fitted to experimental moisture characteristic curve data and combined with saturated hydraulic conductivity from laboratory analysis to estimate unsaturated hydraulic conductivity. Numerical analysis based on moisture profiles and hydraulic properties was used to estimate vertical flux.Grant no. 14-08-0001-G1551-04, Project no. 11; financed in part by the U.S. Dept. of the Interior, Geological Survey, through the Colorado Water Resources Research Institute