Grantee Research Project Results
Final Report: Assessment of Stormwater Harvesting via Managed Aquifer Recharge to Develop New Water Supplies in the Arid West: the Salt Lake Valley Example
EPA Grant Number: R835824Title: Assessment of Stormwater Harvesting via Managed Aquifer Recharge to Develop New Water Supplies in the Arid West: the Salt Lake Valley Example
Investigators: Dupont, R. Ryan , McLean, Joan E , Null, Sarah , Peralta, Richard , Jackson-Smith, Douglas
Institution: Utah State University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2015 through August 31, 2018 (Extended to August 31, 2020)
Project Amount: $749,998
RFA: Human and Ecological Health Impacts Associated with Water Reuse and Conservation Practices (2014) RFA Text | Recipients Lists
Research Category: Human Health , Water
Objective:
The project was designed to test the hypothesis that Managed Aquifer Recharge (MAR) via Green Infrastructure (GI) systems for stormwater harvesting is a technically feasible, socially and environmentally acceptable, economically viable, and regulatorily achievable option for developing new water supplies for arid Western urban ecosystems experiencing increasing population and climate change pressures.
Summary/Accomplishments (Outputs/Outcomes):
Research Component 1, Monitoring of Existing MAR/GI Stormwater Management Systems – Based on MAR/GI system monitoring that took place during the study, a wide range of pollutant concentrations result when data from a range of rainfall events are combined even at a specific site. Analysis of relationships among pollutant runoff concentrations and rainfall event return periods, duration, depth, and Antecedent Dry Day did not result in any statistically significant relationships with rainfall event variables. Repeat measurements at the field sites and roof runoff locations over time indicated that concentrations were consistent, suggesting runoff values generated from this study are representative of specific land use conditions and roofing materials for which they were measured.
Comparison of pore water concentrations at the 300 East bioswale site between BR cells receiving roadway runoff and a control cell receiving only rainfall highlighted the role background soil plays in infiltration water quality at BR sites. This observation also indicated the importance of quantifying background soil pore water concentrations in evaluating the pollutant removal efficiency actually provided by BR systems. At the 300 East site pore water concentrations below the treatment aera were equal or less than pore water concentrations at the control site, indicating complete attenuation of all roadway runoff pollutants up to the maximum loading rates observed during the study. The significance of properties of engineered media on impacting infiltrating water quality was also evident from results of the Public Utilities site. A lack of vegetated treatment area at the site, significant leaching of most pollutants from the utelite expanded shale material used by itself as a storage layer media, and the lack of pollutant removal by the gravel storage layer media indicate both the need for an active vegetation layer, and careful consideration of the leaching potential of engineered material before implementing a BR system using this design approach.
Finally, the importance of vegetation to the overall performance of BR systems was highlighted from the results at the Green Meadows site. Plants were shown to have a significant impact on both nutrient and metal pore water concentrations, with the unplanted control treatment generally having higher concentrations in the pore water than planted treatments. The significant exception was As, where plant root zones appear to have a significant impact on the solubilization of As into soil pore water from the labile As that exists within the native soils common to Northern Utah. Despite mobilization of As within the plant root zone, pore water, soil, and groundwater concentration results indicated that pollutants were not mobilized below the root zone and that these vegetated BR systems are not a source of pollutants to groundwater over the pollutant loading rates measured during the study.
Research Component 2, Integrated Modeling – This study provided an evaluation of the performance of the WinSLAMM model in a region of the U.S. which it has not been validated to date. During the calibration phase, the model did not predict TSS loadings well when using default parameter values. After the concentrations were modified using measured Northern Utah site data, accurate TSS predictions were achieved. On the other hand, TP and TDP concentrations were not accurately estimated by WinSLAMM with any of the model parameter files, default or modified. Constant concentrations in the default files, independent of rainfall depth were much lower than the values observed from the Northern Utah sites, and observed pollutant runoff data did vary with rainfall depth. Both TP and TDP model predictions were improved by using the TSS pollutant loadings predicted from the WinSLAMM model using field site modified parameter files and the TP/TSS and TDP/TP ratios observed from measured data.
Runoff coefficients calibrated for the Logan sites did not describe runoff observed at the Salt Lake Valley sites. Moreover, the behavior of the two Salt Lake Valley sites were very different from each other, and a combined calibration for the Red Butte Creek watershed sites was not possible. Site-specific runoff coefficient calibration appears to be necessary for the application of WinSLAMM in the Northern Utah region.
Three scenarios of GI implementation were analyzed in the Red Butte watershed to assess their impact on runoff volume and pollutant concentration changes. When implementing GI for a small portion (10%) of the connected impervious areas the greatest volume reduction was predicted when roof runoff was treated, while the best solid loadings reduction was produced when street runoff was treated. For the 50% GI implementation scenarios, runoff reduction was similar no matter the surface type being treated. However, there was a large difference in TSS reduction with GI applied to varying surface types. Implementing GI for streets produced larger particulate solids loading reductions than when treating roofs, which corresponds to results found by others. The percent reduction of TSS and TP estimated for the 100% scenario corresponded to results reported in the literature. However, volume reductions (78% to 84%) were much higher than what has been previously reported (50% to 64%). The benefits of GI for both the 10% and 50% implementation options vary depending on the surface type treated, and the decision of what GI technique to implement depends on the reduction objectives, i.e., runoff volume versus pollutant load reductions.
Overall, green infrastructure alternatives evaluated for ecosystem services benefits at the site, subbasin and watershed scales all reduce total phosphorus concentration and exhibit a water quality improvement service. In spring simulations, green infrastructure captures runoff to mitigate flooding. Often in these alternatives, stream temperature is increased, and dissolved oxygen is decreased. The findings for changes in stream temperature and dissolved oxygen show that atmospheric heating drive these effects. Reach scale alternatives also highlight the differences between green infrastructure types and their deliveries of different ecosystem services. Rain gardens reduce streamflow the most, which is beneficial for flood mitigation during spring runoff conditions, but not during summer baseflow conditions when more streamflow is beneficial. Grass swales reduce total phosphorus to the stream the most and decrease streamflow the least.
The Red Butte Creek models were connected to an existing Jordan River model to provide insight on the effects of green stormwater infrastructure for aquatic habitats in the Jordan River and Great Salt Lake. Green infrastructure alternatives at the watershed-scale demonstrate that implementation of green infrastructure in multiple sub-watersheds is needed to produce a noticeable change downstream in the larger basin. Specifically, the implementation of green infrastructure across 13% of the urban area in the Red Butte Creek watershed, or 0.23 mi2 (147 ac) of roofs, streets, and parking lots, leads to fractions of a percentage change for streamflow, total phosphorus concentration, stream temperature, and dissolved oxygen at the end of the Jordan River model, Great Salt Lake. These effects are less than the model error, indicating nonsignificance. To see measurable change, at least 13% of all urban areas, or 1.36 mi2 (870 ac) total roofs, parking lots, and streets must be implemented with green infrastructure in the seven canyon creek watersheds. Specifically, green infrastructure implementation in the seven canyon creek watersheds lead to at most about a 9.5% (0.23 m3/s) reduction in streamflow, a 17.4% (0.24°C) reduction in stream temperature, a 1.3% (0.13 mg/L) increase in dissolved oxygen concentration, and a 1.2% (4.5 μg/L) reduction in total phosphorus concentration in the winter/spring Jordan River model. In the late summer Jordan River model, there is at most about a 9.3% (0.41 m3/s) decrease in streamflow and an 8.6% (57.4 μg/L) reduction in total phosphorus concentration.
To provide an independent evaluation of the impact on stormwater runoff and groundwater recharge through the implementation of GI systems at a subbasin scale, a recalibrated HSPF model of the Salt Lake County watershed and one of its subbasins was use for a range of rainfall and stormwater recovery scenarios. When GI was applied to the full basin only a slight decrease in total annual discharge was observed. Application of GI within a more urbanized subbasin resulted in significantly reduced peak runoff and appreciably increased groundwater recharge, consistent with WinSLAMM modeling results in the Red Butte Creek study area.
To illustrate the practical application of WinSLAMM to model stormwater runoff and infiltration for secondary recovery, a case study in the Salt Lake Valley near the Jordan River was carried out to evaluate the potential for Spring runoff infiltration through shallow groundwater recharge coupled with Summer groundwater recovery for turf grass irrigation under Northern Utah climatic conditions (historical April, May, early June rainfall patterns). Results indicated a stormwater recovery effectiveness from 10.7% to 52.7% depending on irrigation scheduling, and a feasible constant recovery rate of shallow groundwater from 1.0 to 10.6 gpm. At these recovery rates, from 5 to 57% of the small landscape area of the modeled development could be irrigated with this harvested stormwater.
Research Component 3, Social Science Research There is a growing understanding of and interest in methods to use distributed systems to capture stormwater on-site in Utah.
Concerns about potential groundwater contamination from any of the infiltration-oriented MAR/GI systems included in the interviews with key informants outweighed perceived advantages relative to boosting scarce potable water supplies.
There is much more receptivity (and fewer concerns) about approaches that rely on infiltration and recharge of shallow (non-culinary) aquifers, with some preference for subsurface storage/infiltration systems as being more acceptable to local residents, developers, and politicians, when a broader representation of stakeholders was interviewed through the on-line survey. A lack of data on stormwater GI BMP performance in their area was reported by roughly half of the cities.
Results from the household surveys demonstrated that individual residents are largely unaware of how stormwater is handled in their neighborhoods. In cases where GI has been deployed, subsurface storage/infiltration was well regarded, while surface storage/infiltration systems had a more uneven track record (mainly because of poor design, implementation or maintenance).
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 22 publications | 2 publications in selected types | All 2 journal articles |
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Prudencio L, Null SE. Stormwater management and ecosystem services: a review. Environmental Research Letters 2018;13(3):033002. |
R835824 (2018) R835824 (Final) |
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Zhang J, Peralta RC. Estimating infiltration increase and runoff reduction due to green infrastructure. Journal of Water and Climate Change 2019;10(2):237-242. |
R835824 (Final) |
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Supplemental Keywords:
stormwater, aquifer recharge, groundwater, green infrastructure, ecosystem services, modelingProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
- 2019 Progress Report
- 2018 Progress Report
- 2017 Progress Report
- 2016 Progress Report
- Original Abstract
2 journal articles for this project