Dahl, T.A., Kendall, A.D., and D.W. Hyndman (2018). Impacts of projected climate change on sediment yield and dredging costs. Hydrological Processes, (February), 1223–1234. http://doi.org/10.1002/hyp.11486

Abstract

Changes in climate may significantly affect how sediment moves through watersheds into harbours and channels that are dredged for navigation or flood control. Here, we applied a hydrologic model driven by a large suite of climate change scenarios to simulate both historical and future sediment yield and transport in two large, adjacent watersheds in the Great Lakes region. Using historical dredging expenditure data from the U.S. Army Corps of Engineers, we then developed a pair of statistical models that link sediment discharge from each river to dredging costs at the watershed outlet. Although both watersheds show similar slight decreases in streamflow and sediment yield in the near-term, by Mid-Century, they diverge substantially. Dredging costs are projected to change in opposite directions for the two watersheds; we estimate that future dredging costs will decline in the St. Joseph River by 8-16% by Mid-Century but increase by 1-6% in the Maumee River. Our results show that the impacts of climate change on sediment yield and dredging may vary significantly by watershed even within a region and that agricultural practices will play a large role in determining future streamflow and sediment loads. We also show that there are large variations in responses across climate projections that cause significant uncertainty in sediment and dredging projections.

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Kuhl, A.S., Kendall, A.D., Van Dam, R.L., and Hyndman, D.W. (2018). Quantifying Soil Water and Root Dynamics Using a Coupled Hydrogeophysical Inversion. Vadose Zone Journal, 17(1). http://doi.org/10.2136/vzj2017.08.0154

Abstract

Plot- to field-scale root distribution data are relatively rare and difficult to measure with traditional methods. Nevertheless, these data are needed to accurately model root water uptake (RWU) processes within agronomic, hydrologic, and terrestrial biosphere models. New tools are needed to effectively observe root distributions and model dynamic root growth processes. In the past decade, geophysical tools have increasingly been used to study the vadose zone, and hydrogeophysical inversions have shown promise to noninvasively characterize water dynamics. In such an approach, the hydrology is modeled and hydrological data are inverted with the geophysical data, constraining the geophysical inversion results and decreasing uncertainty and the number of nonunique solutions. In this study, we developed and tested a coupled hydrogeophysical inversion approach that uses electrical resistivity data to estimate soil hydraulic, petrophysical, and root dynamic parameters. This builds on prior research that used either a coupled hydrogeophysical inversion to estimate soil hydraulic parameters only, or a hydrological inversion to estimate root distribution or root water uptake parameters. Our results indicate that under the conditions tested, this approach accurately captures root water dynamics and soil hydraulic parameters. This opens up opportunities to noninvasively image a variety of root distributions and soil systems, better understand the dynamics of RWU processes, and improve estimates of transpiration for systems models.

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Pokhrel, Y.; Burbano, M.; Roush, J.; Kang, H.; Sridhar, V.; Hyndman, D.W. (2018). A Review of the Integrated Effects of Changing Climate, Land Use, and Dams on Mekong River Hydrology. Water 2018, 10, 266. doi:10.3390/w10030266

Abstract

The ongoing and proposed construction of large-scale hydropower dams in the Mekong river basin is a subject of intense debate and growing international concern due to the unprecedented and potentially irreversible impacts these dams are likely to have on the hydrological, agricultural,and ecological systems across the basin.  Studies have shown that some of the dams built in the tributaries and the main stem of the upper Mekong have already caused basin-wide impacts by altering the magnitude and seasonality of flows, blocking sediment transport, affecting fisheries and livelihoods of downstream inhabitants, and changing the flood pulse to the Tonle Sap Lake.There are hundreds of additional dams planned for the near future that would result in further changes, potentially causing permanent damage to the highly productive agricultural systems and fisheries, as well as the riverine and floodplain ecosystems.  Several studies have examined the potential impacts of existing and planned dams but the integrated effects of the dams when combined with the adverse hydrologic consequences of climate change remain largely unknown.  Here, we provide a detailed review of the existing literature on the changes in climate, land use, and dam construction and the resulting impacts on hydrological, agricultural, and ecological systems across the Mekong.  The review provides a basis to better understand the effects of climate change and accelerating human water management activities on the coupled hydrological-agricultural-ecological systems, and identifies existing challenges to study the region’s Water, Energy, and Food (WEF) nexus with emphasis on the influence of future dams and projected climate change. In the last section, we synthesize the results and highlight the urgent need to develop integrated models to holistically study the coupled natural-human systems across the basin that account for the impacts of climate change and water infrastructure development. This review provides a framework for future research in the Mekong, including studies that integrate hydrological, agricultural, and ecological modeling systems.

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Partridge, T.F., Winter, J.M., Osterberg, E.C., Hyndman, D.W., Kendall, A.D., and Magilligan, F.J. (2018). Spatially Distinct Seasonal Patterns and Forcings of the U.S. Warming Hole. Geophysical Research Letters, 45(4), 2055–2063. http://doi.org/10.1002/2017GL076463

Abstract

We present a novel approach to characterize the spatiotemporal evolution of regional cooling across the eastern United States (commonly called the U.S. warming hole), by defining a spatially explicit boundary around the region of most persistent cooling. The warming hole emerges after a regime shift in 1958 where annual maximum (T max ) and minimum (T min ) temperatures decreased by 0.83°C and 0.46°C, respectively. The annual warming hole consists of two distinct seasonal modes, one located in the southeastern United States during winter and spring and the other in the midwestern United States during summer and autumn. A correlation analysis indicates that the seasonal modes differ in causation. Winter temperatures in the warming hole are significantly correlated with the Meridional Circulation Index, North Atlantic Oscillation, and Pacific Decadal Oscillation. However, the variability of ocean-atmosphere circulation modes is insufficient to explain the summer temperature patterns of the warming hole.

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Benson, D., D. Ding, D. Fernàndez-Garcia, C. Henri, D.W. Hyndman, M. Phanikumar, and D. Bolster, 2017, Elimination of the reaction ‘scale effect’: Application of the Lagrangian reactive particle-tracking method to simulate mixing-limited, field-scale biodegradation at the Schoolcraft (MI) site, Water Resources Research, doi: 10.1002/2017WR021103

Abstract

Measured (or empirically fitted) reaction rates at groundwater remediation sites are typically much lower than those found in the same material at the batch or laboratory scale. The reduced rates are commonly attributed to poorer mixing at the larger scales. A variety of methods have been proposed to account for this scaling effect in reactive transport. In this study, we use the Lagrangian particle-tracking and reaction (PTR) method to simulate a field bioremediation experiment at the Schoolcraft, MI site. A denitrifying bacterium, Pseudomonas Stutzeri strain KC (KC), was injected to the aquifer, along with sufficient substrate, to degrade the contaminant, carbon tetrachloride (CT), under anaerobic conditions. The PTR method simulates chemical reactions through probabilistic rules of particle collisions, interactions, and transformations to address the scale effect (lower apparent reaction rates for each level of upscaling, from batch to column to field scale). In contrast to a prior Eulerian reaction model, the PTR method is able to match the fieldscale experiment using the rate coefficients obtained from batch experiments.

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Wood W.W., Hyndman D.W. (2017) Groundwater Depletion : A Significant Unreported Source of Atmospheric Carbon Dioxide, Earth’s Future 3: 10–12, DOI:10.1002/eft2.259

Abstract

Quantifying the annual flux of CO2 (carbon dioxide) and equivalent emissions to the atmosphere is critical for both policy decisions and modeling of future climate change. Given the importance of greenhouse gas emissions to climate change and a recognized mismatch between sources and sinks (e.g., Liu & Dreybrodt, 2015), it is important to quantify these parameters. A significant and previously unrecognized CO2 contribution arises from groundwater depletion (net removal from storage). The average annual 1.7MMT (million metric tons) CO2 released in the United States from this source is greater than approximately one third of the 23major sources reported by the US EPA (United States Environmental Protection Agency) to the IPCC (Intergovernmental Panel on Climate Change; US EPA, 2016).

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Deines J.M., Kendall A.D., Hyndman D.W. (2017) Annual irrigation dynamics in the US Northern High Plains derived from Landsat satellite data. Geophysical Research Letters. DOI: 10.1002/2017GL074071

Abstract

Sustainable management of agricultural water resources requires improved understanding of irrigation patterns in space and time. We produced annual, high-resolution (30 m) irrigation maps for 1999–2016 by combining all available Landsat satellite imagery with climate and soil covariables in Google Earth Engine. Random forest classification had accuracies from 92 to 100% and generally agreed with county statistics (r2 = 0.88–0.96). Two novel indices that integrate plant greenness and moisture information show promise for improving satellite classification of irrigation. We found considerable interannual variability in irrigation location and extent, including a near doubling between 2002 and 2016. Statistical modeling suggested that precipitation and commodity price influenced irrigated extent through time. High prices incentivized expansion to increase crop yield and profit, but dry years required greater irrigation intensity, thus reducing area in this supply-limited region. Data sets produced with this approach can improve water sustainability by providing consistent, spatially explicit tracking of irrigation dynamics over time.

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Hyndman, D.W., T.Xu, J.M. Deines, G. Cao, R. Nagelkirk, A. Vina, W. McConnell, B. Basso, A.D. Kendall, S. Li, L. Luo, F. Lupi, J.A. Winkler, W. Yang, C. Zheng, and J. Liu, (2017), Quantifying changes in water use and groundwater availability in a megacity using novel integrated systems modeling. Geophysical Research Letters. DOI: 10.1002/2017GL074429

Abstract

Water sustainability in megacities is a growing challenge with far-reaching effects. Addressing sustainability requires an integrated, multidisciplinary approach able to capture interactions among hydrology, population growth, and socioeconomic factors and to reflect changes due to climate variability and land use. We developed a new systems modeling framework to quantify the influence of changes in land use, crop growth, and urbanization on groundwater storage for Beijing, China. This framework was then used to understand and quantify causes of observed decreases in groundwater storage from 1993 to 2006, revealing that the expansion of Beijing’s urban areas at the expense of croplands has enhanced recharge while reducing water lost to evapotranspiration, partially ameliorating groundwater declines. The results demonstrate the efficacy of such a systems approach to quantify the impacts of changes in climate and land use on water sustainability for megacities, while providing a quantitative framework to improve mitigation and adaptation strategies that can help address future water challenges.

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Hyndman et al. – 2017 – Quantifying changes in water use and groundwater availability in a megacity using a novel integrated systems model

Cotterman, K.A., Kendall, A.D., Basso, B., Hyndman, D.W. (2017). Climatic Change. DOI: 10.1007/s10584-017-1947-7

Abstract

Crop production in the Central High Plains is at an all-time high due to increased demand for biofuels, food, and animal products. Despite the need to produce more food by mid-century to meet expected population growth, under current management and genetics, crop production is likely to plateau or decline in the Central High Plains due to groundwater withdrawal at rates that greatly exceed recharge to the aquifer. The Central High Plains has experienced a consistent decline in groundwater storage due to groundwater withdrawal for irrigation greatly exceeding natural recharge. In this heavily irrigated region, water is essential to maintain yields and economic stability. Here, we evaluate how current trends in irrigation demand may impact groundwater depletion and quantify the impacts of these changes on crop yield and production through to 2099 using the well-established System Approach to Land Use Sustainability (SALUS) crop model. The results show that status quo groundwater management will likely reduce irrigated corn acreage by ~60% and wheat acreage by ~50%. This widespread forced shift to dryland farming, coupled with the likely effects of climate change, will contribute to overall changes in crop production. Taking into account both changes in yield and available irrigated acreage, corn production would decrease by approximately 60%, while production of wheat would remain fairly steady with a slight increase of about 2%.

Cotterman et al. – 2017 – Groundwater depletion and climate change future prospects of crop production in the Central High Plains Aquife