The Role of the Unsaturated Zone in Artificial Recharge at San Gorgonio Pass, California

Ellett, Kevin

doi:10.2136/vzj2004.0763

Cited by 17 publications

(30 citation statements)

References 7 publications

(9 reference statements)

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“…Most recent perched-water zone studies have been conducted in the context of contaminant transport; however, the effects of perching phenomena are also of interest in artificial recharge efforts (Flint et al 2004(Flint et al , 2012 and for lateral flow on hillslopes (Uchida et al 2004) and reclaimed soils (Kellin et al 2004). Generally, artificial recharge projects apply water in surface and near-surface spreading locations, using the vadose zone to transport and store water.…”

Section: Overview Of Perched Water Literaturementioning

confidence: 99%

“…Generally, artificial recharge projects apply water in surface and near-surface spreading locations, using the vadose zone to transport and store water. Flint et al (2004) used a numerical analysis to demonstrate that recharge of the regional aquifer at San Gorgonio Pass, California, could be ineffective because most of the injected water would remain above a large perching zone, considerably delaying and limiting recharge to occur in relatively small areas. A follow-up study (Flint et al 2012) showed that, after actual infiltration of almost 4 million m 3 of water, vertical aquifer recharge was considerably larger than predicted.…”

Section: Overview Of Perched Water Literaturementioning

confidence: 99%

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Perched-Water Evaluation for the Deep Vadose Zone Beneath the B, BX, and BY Tank Farms Area of the Hanford Site

Truex¹,

Oostrom²,

Carroll³

et al. 2013

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Executive SummaryPerched-water conditions have been observed in the vadose zone above a fine-grained zone that is located a few meters above the water table within the B, BX, and BY Tank Farms area. The perched water contains elevated concentrations of uranium and technetium-99. This perched-water zone is important to consider in evaluating the future flux of contaminated water into the groundwater. The study described in this report was conducted to examine the perched-water conditions and quantitatively evaluate 1) factors that control perching behavior, 2) contaminant flux toward groundwater, and 3) associated groundwater impact.A perched-water zone in the subsurface is defined as a saturated zone that is above or not directly connected to the regional water table. Perching phenomena may occur in a permeable layer overlaying a relatively impermeable layer. A perched-water zone develops when saturated conditions above a lowpermeability layer are needed to move infiltrating water vertically through this layer. Water infiltrating through the vadose zone encounters a resistance at a low-permeability layer and must build up pressure, in the form of a perched-water head, to conduct water through the layer. Over time, the perched-water system may reach an equilibrium condition where the rate of infiltration equals the rate of water moving out of the perched-water zone and deeper toward the groundwater. Perched water can occur under natural recharge conditions and the perched-water height would remain essentially constant over time if the infiltration rate from the surface remained constant. Transient perched-water zones can also occur when infiltration at the surface is increased due to surface disturbance (e.g., removal of vegetation or construction activities) or due to a discharge of water (or aqueous waste). When the overall system recharge rate is increased, perched water may form and then persist until recharge is reduced or water discharge is terminated and the impact of excess water in the vadose zone dissipates. At the B, BX, and BY Tank Farms area, both of these factors may have contributed to forming the current perched water.The presence of perched water enables use of a pumping system for removal of contaminant mass from the subsurface to decrease the total contaminant mass that would eventually move into the groundwater. Under most of the tested scenarios, the perched water is a transient condition, although continuation of current disturbed-surface recharge conditions for the B, BX, and BY Tank Farms area may maintain the perched-water zone to some extent even as the impacts of historical waste and water discharges dissipate. For transient perched-water conditions, especially when coupled with a decreased recharge rate (and/or dissipation of previous waste and water discharges), declining perched-water height will render removal of perched water more difficult with time. As such, near-term actions to remove perched water will be more effective. Removal of perched water by pumping would hasten the tran...

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Section: Overview Of Perched Water Literaturementioning

confidence: 99%

Section: Overview Of Perched Water Literaturementioning

confidence: 99%

Perched-Water Evaluation for the Deep Vadose Zone Beneath the B, BX, and BY Tank Farms Area of the Hanford Site

Truex¹,

Oostrom²,

Carroll³

et al. 2013

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show abstract

“…With such approaches use is made of some measured vadose zone property which is modelled using a transport model in which the travel time is considered, directly or indirectly, as the fitting model parameter. With the inverse approach, measured moisture content or resident tracer profiles have been used as fitting data by Wang et al [49], McElroy and Hubbell [32], Hubbell et al [17], Flint and Ellett [13] and Wu et al [50]. Robinson et al [39] combines measurements of moisture content with the analysis of a tracer experiment.…”

Section: Introductionmentioning

confidence: 99%

Estimating travel time of recharge water through a deep vadose zone using a transfer function model

Mattern

Vanclooster

2009

Environ Fluid Mech

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We estimate the travel time of percolating water through a deep vadose zone at the regional scale using a transfer function model and a physical based conceptual flow model (Hydrus-1D), thereby exploiting the time series of precipitation, actual evapotranspiration and groundwater piezometry and generic vadose zone data. With the transfer function model we observe a high variability of estimated travel time varying from 0.9 to 3.1 years, corresponding to estimated vertical water flux velocities varying from 6.6 to 28.0 m/year. These results were compared with the travel time estimated from the physical based conceptual model. With the flow model, estimated travel time varies between 4.7 and 15.5 years, corresponding to water flux velocities varying between 1.7 and 4.1 m/year. The estimated travel time calculated with the flow model were therefore about five times larger than those estimated with the transfer function model. This could be explained by the fact that the transfer function model considers heterogeneous recharge from the vadose zone as well as from the vicinity of the piezometer through the so called "pushing effect". In addition, the flow model requires various hydrogeological and hydrodynamic parameters which were estimated using generic parametrisation approaches, that are largely affected by uncertainty and may not reflect the local conditions. In contrast, the transfer function model only exploits available measurable time series and has the advantage of being site-specific.

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“…Water infiltrated from ponds in areas underlain by thick unsaturated zones having less permeable deposits than those found along major streams and rivers may be a feasible method of recharging underlying alluvial aquifers. Some of the difficulties inherent with this approach and the role of thick unsaturated zones in artificial recharge were studied numerically by Flint and Ellett (2004). However, few field‐scale experiments are reported in the literature describing the movement, and associated changes in quality, of water infiltrated from ponds through thick, heterogeneous unsaturated zones.…”

Section: Introductionmentioning

confidence: 99%

Artificial Recharge Through a Thick, Heterogeneous Unsaturated Zone

Izbicki¹,

Flint

Stamos

2008

Groundwater

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Thick, heterogeneous unsaturated zones away from large streams in desert areas have not previously been considered suitable for artificial recharge from ponds. To test the potential for recharge in these settings, 1.3 x 10(6) m(3) of water was infiltrated through a 0.36-ha pond along Oro Grande Wash near Victorville, California, between October 2002 and January 2006. The pond overlies a regional pumping depression 117 m below land surface and is located where thickness and permeability of unsaturated deposits allowed infiltration and saturated alluvial deposits were sufficiently permeable to allow recovery of water. Because large changes in water levels caused by nearby pumping would obscure arrival of water at the water table, downward movement of water was measured using sensors in the unsaturated zone. The downward rate of water movement was initially as high as 6 m/d and decreased with depth to 0.07 m/d; the initial time to reach the water table was 3 years. After the unsaturated zone was wetted, water reached the water table in 1 year. Soluble salts and nitrate moved readily with the infiltrated water, whereas arsenic and chromium were less mobile. Numerical simulations done using the computer program TOUGH2 duplicated the downward rate of water movement, accumulation of water on perched zones, and its arrival at the water table. Assuming 10 x 10(6) m(3) of recharge annually for 20 years, a regional ground water flow model predicted water level rises of 30 m beneath the ponds, and rises exceeding 3 m in most wells serving the nearby urban area.

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The Role of the Unsaturated Zone in Artificial Recharge at San Gorgonio Pass, California

Cited by 17 publications

References 7 publications

Perched-Water Evaluation for the Deep Vadose Zone Beneath the B, BX, and BY Tank Farms Area of the Hanford Site

Perched-Water Evaluation for the Deep Vadose Zone Beneath the B, BX, and BY Tank Farms Area of the Hanford Site

Estimating travel time of recharge water through a deep vadose zone using a transfer function model

Artificial Recharge Through a Thick, Heterogeneous Unsaturated Zone

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