Zhang F.,Pacific Northwest National Laboratory |
Ward A.L.,Pacific Northwest National Laboratory |
Keller J.M.,GeoSystems Analysis Inc
Vadose Zone Journal | Year: 2011
Gravel and coarse sand make up significant portions of some environmentally important sediments, but the hydraulic properties of the sediments are typically obtained in the laboratory using only the fine fraction (e.g., <2 mm or 4.75 mm). Researchers have found that the gravel content has a significant impact on the hydraulic properties of bulk soils. Therefore, laboratory experiments were conducted to measure the porosity and the saturated hydraulic conductivity of binary mixtures with different fractions of coarse and fine components. We proposed a mixing-coefficient model to estimate the porosity and a power-averaging method to determine the effective grain diameter of sediments. These were used to predict the saturated hydraulic conductivity of binary mixtures. The proposed methods could describe the porosity and saturated hydraulic conductivity of the binary mixtures for a range of gravel contents, and they were successfully applied to two data sets in the literature. © Soil Science Society of America.
Zhan G.,SALt Inc |
Keller J.,GeoSystems Analysis Inc |
Milczarek M.,GeoSystems Analysis Inc |
Giraudo J.,SALt Inc
Mine Water and the Environment | Year: 2014
The AA Leach Pad at Barrick Goldstrike Mine was reclaimed using an evapotranspiration (ET) cover designed to limit the infiltration of precipitation into the facility. Water content and matric potential sensor stations were installed in the cover and underlying leach material after cover system placement. Monitoring of the sensor nests continued for 11 years. Data indicates that the cover is performing well, limiting net percolation to less than 1 % of annual precipitation. The AA Leach Pad is the first large-scale closed mine waste facility that has been robustly monitored for a relatively long time in Nevada, USA. The results provide an understanding of ET cover system performance for closure of mine waste facilities and offer guidance for ET cover system requirements in other arid regions. © Springer-Verlag Berlin Heidelberg 2014.
Scherberg J.,GeoSystems Analysis Inc |
Baker T.,Walla Walla Basin Watershed Council |
Selker J.S.,Oregon State University |
Henry R.,Walla Walla Basin Watershed Council
Water Resources Management | Year: 2014
The Walla Walla Basin, in Eastern Oregon and Washington, USA, faces challenges in sustaining an agricultural water supply while maintaining sufficient flow in the Walla Walla River for endangered fish populations. Minimum summer river flow of 0.71 m3/s is required, forcing irrigators to substitute groundwater from a declining aquifer for lost surface water diversion. Managed Aquifer Recharge (MAR) was initiated in 2004 attempting to restore groundwater levels and improve agricultural viability. The Integrated Water Flow Model (IWFM) was used to compute surface and shallow groundwater conditions in the basin under water management scenarios with varying water use, MAR, and allowable minimum river flow. A mean increase of 1.5 m of groundwater elevation, or 1.5 % of total aquifer storage, was predicted over the model area when comparing maximum MAR and no MAR scenarios where minimum river flow was increased from current level. When comparing these scenarios a 53 % greater summer flow in springs was predicted with the use of MAR. Results indicate MAR can supplement irrigation supply while stabilizing groundwater levels and increasing summer streamflow. Potential increase in long-term groundwater storage is limited by the high transmissivity of the aquifer material. Increased MAR caused increased groundwater discharge through springs and stream beds, benefiting aquatic habitat rather than building long-term aquifer storage. Judicious siting of recharge basins may be a means of increasing the effectiveness of MAR in the basin. © 2014, Springer Science+Business Media Dordrecht.
Bunting D.P.,University of Arizona |
Kurc S.,University of Arizona |
Grabau M.,GeoSystems Analysis Inc
River Research and Applications | Year: 2013
Human disturbances have contributed to the deterioration of many western US rivers in the past century. Cottonwood-willow communities, present historically along the Colorado River, protect watersheds and provide wildlife habitat, but are now among the most threatened forests. As a result, restoration efforts have increased to re-establish and maintain cottonwood-willow stands. While successful establishment has been observed using multiple strategies with varying investments, few projects are evaluated to quantify efficacy and determine long-term sustainability. We monitored a seeded cottonwood-willow site over a five-year period beginning in 2007, with particular interest in how density affected vegetation diversity and stand structure over time. Fremont cottonwood (Populus fremontii) and volunteer tamarisk (Tamarix ramosissma) were the only abundant riparian trees at the site after one year. P. fremontii, compared to T. ramosissma, had higher growth rates, lower mortality, and dominated overstory and total cover each year. Vegetation diversity decreased from 2007-2009, but was similar from 2009-2011 as a result of decreased herbaceous and increased shrub species richness. Diversity was highest in the lowest density class (1-12 stems/m2), but similar among all other classes (13-24, 25-42, 43+). High initial woody species densities resulted in single-stemmed trees with depressed terminal and radial growths. Allometry, relating height to DBH at different densities, could prove to be an important tool for long-term restoration management and studying habitat suitability. Understanding long-term trends at densely-planted or seeded sites can benefit restoration managers who aim to establish specific community structure and vegetation diversity for wildlife habitat. © 2012 John Wiley & Sons, Ltd.
Keller J.,GeoSystems Analysis Inc. |
Milczarek M.,GeoSystems Analysis Inc. |
Yao T.M.,GeoSystems Analysis Inc. |
Buchanan M.,GeoSystems Analysis Inc.
Tailings and Mine Waste'10 - Proceedings of the 14th International Conference on Tailings and Mine Waste | Year: 2011
Mine tailing properties significantly differ from other mine waste (e.g. waste rock and heap leach material) such that cover system design criteria for cover success and post-closure monitoring should require different approaches. Tailings can generally be classified into three material types corresponding to location within the impoundment, with each material type possessing distinct physical and hydraulic properties. Finding from tailings reclamation research and performance monitoring at five tailings facilities in the southwestern United States indicate that: (1) alternative cover system designs based on location within the impoundment can maximize performance (and reduce costs), (2) tailings underlying shallow evapotranspirative cover systems play a significant role in reducing net percolation, whether they are non-acid or acid, and (3) depending on the cover material properties and climate, monolayer covers over acid tailings may show limited acidification and salinization. Consequently, tailings cover system design should consider potential interactions between the tailings, cover material and vegetation. © 2011 Taylor & Francis Group, London.
Bunting D.P.,University of Arizona |
Kurc S.A.,University of Arizona |
Grabau M.R.,GeoSystems Analysis Inc.
Journal of Arid Environments | Year: 2011
Dryland riparian restoration often requires the use of large amounts of surface water. Retired agricultural fields located on floodplains associated with shallow water tables may minimize water requirements for restoration because irrigation could be ceased when target species become phreatophytic. Using existing agricultural infrastructure, we implemented two irrigation treatments over two years to promote native Fremont cottonwood (Populus fremontii) establishment over non-native tamarisk (Tamarix ramosissima): (1) frequent shallow irrigation; and (2) infrequent deep irrigation. We assessed how these treatments: (a) contributed to above- and below-ground growth of native and non-native species; (b) promoted native species survival; and (c) supported a competitive advantage of P. fremontii over T. ramosissima. Overall growth rates were highest one year after seeding, and average P. fremontii growth rates were higher than T. ramosissima in both years. Overall P. fremontii mortality was lower than T. ramosissima in both years. P. fremontii crown cover consistently increased and was ultimately the most abundant species in the overstory. Our results suggest that P. fremontii can out-compete T. ramosissima in these retired agricultural settings. In addition, this study suggests that irrigation frequency can be further decreased while reducing irrigation input, thus minimizing both effort and surface water required for restoration. © 2011 Elsevier Ltd.