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.

Article
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

 

Luscz, E.C., Kendall, A.D., and D.W. Hyndman, (2017), A spatially explicit statistical model to quantify nutrient sources, pathways, and delivery at the regional scale, Biogeochemistry: 133(1), 37-57, DOI: 10.1007/s10533-017-0305-1

Abstract

Nutrient loading has been linked to many issues including eutrophication, harmful algal blooms, and decreases in aquatic species diversity. In order to develop mitigation strategies to control nutrient sources, the relative contribution and spatial distribution of nutrient sources must be quantified. Though many watershed nutrient models exist in the literature, there is generally a tradeoff between the scale of the model and the level of detail regarding the individual sources of nutrients and basin transport and fate characteristics. To examine the link between watershed nutrient sources, landscape processes, and in-stream loads in the Lower Peninsula of Michigan, a spatially explicit nutrient loading model was developed. The model uses spatially explicit descriptions of nutrient sources and a novel statistical model describing spatially-explicit nutrient attenuation along transport pathways to predict total nitrogen and phosphorus loads. Observations collected during baseflow and melt conditions from 2010–2012 were used to calibrate and validate the model. The model predicts nutrient loads, provides information on the sources of nutrients within each watershed, and estimates the relative contribution of different sources to the overall nutrient load. The model results indicate that there is a high degree of variability in seasonal nutrient export rates, which can be significantly greater during snow melt conditions than during baseflow. In addition, the model highlights the considerable variability in seasonal pathways and processes that impact nutrient delivery. The model performance compares favorably to other regional scale nutrient models. This work has the potential to provide valuable information to environmental managers regarding how and where to target efforts to reduce nutrient loads in surface water.

Luscz, Kendall, Hyndman – 2017 – A spatially explicit statistical model to quantify nutrient sources, pathways , and delivery at the reg.

Gómez-Hernández, J. J., J. Butler, A. Fiori, D. Bolster, V. Cvetkovic, G. Dagan, D. Hyndman, 2017, Introduction to special section on modeling highly heterogeneous aquifers: Lessons learned in the last 30 years from the MADE experiments and others, Water Resources Research, doi:10.1002/2017WR020774.

Abstract

During the sessions of the AGU Chapman Conference ‘‘The MADE Challenge for Groundwater Transport in Highly Heterogeneous Aquifers: Insights from 30 Years of Modeling and Characterization at the Field Scale and Promising Future Directions’’ held in Valencia (Spain) on 5–8 October 2015 [Gomez-Hernandez et al., 2016], there was a heated debate on how heterogeneous an aquifer must be to be called ‘‘highly’’ heterogeneous. Is the heterogeneity within a hydrofacies what matters, or is it that across different hydrofacies? For many years, there was general agreement that if the variance of the logarithm of hydraulic conductivity (henceforth, log conductivity) is below one, the aquifer is, at most, mildly heterogeneous, whereas when it is above that level—especially when it is above two— the aquifer is highly heterogeneous. But this variance limit was related to the restrictions imposed by approximations invoked for the analytical solution of the stochastic flow and transport equations, and not what is observed in natural systems. Thus, when dealing with natural systems, do we need to redefine what is meant by ‘‘highly’’ heterogeneous? More than 25 years ago, field experiments began at the MAcroDispersion Experiment (MADE) site in Columbus, Mississippi, a site with an initially reported log conductivity variance above 4. The objective was to improve understanding of solute transport in highly heterogeneous natural systems. As a result of the MADE experiments and related work, it is now generally accepted that heterogeneity has a large impact on subsurface flow and transport processes. Moreover, we now recognize that the variance of log conductivity will be seldom below 1, and we should not be surprised by variances greater than 10. Although our understanding of the role of heterogeneity on flow and transport processes continues to improve, our ability to address practical issues, such as remediation of sites of groundwater contamination, continues to be stymied by heterogeneity. How can we translate our improved understanding of the impact of heterogeneity to address societal expectations for our discipline? These and related questions were discussed at length in the Valencia Chapman conference and prompted the preparation of this special issue on characterization and modeling of highly heterogeneous aquifers. The section is composed of seven papers, some of them corresponding to presentations at the conference and some contributed by authors whose interests parallel those of conference attendees. The range of topics covered by the papers is broad and only reflects a small portion of those covered at the Chapman conference; yet, they demonstrate the high level of interest that the MADE experiments continue to generate in the hydrological community.

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Martin, S.L., Hayes, D.B., Kendall, A.D., and D.W. Hyndman, (2017), The land-use legacy effect: Towards a mechanistic understanding of time-lagged water quality responses to land use/cover, Science of the Total Environment 579: 1794-1803, DOI: 10.1016/j.scitotenv.2016.11.158

Abstract

Numerous studies have linked land use/land cover (LULC) to aquatic ecosystem responses, however only a few have included the dynamics of changing LULC in their analysis. In this study, we explicitly recognize changing LULC by linking mechanistic groundwater flow and travel time models to a historical time series of LULC, creating a land-use legacy map. We then illustrate the utility of legacy maps to explore relationships between dynamic LULC and lake water chemistry. We tested two main concepts about mechanisms linking LULC and lake water chemistry: groundwater pathways are an important mechanism driving legacy effects; and, LULC over multiple spatial scales is more closely related to lake chemistry than LULC over a single spatial scale. We applied statistical models to twelve water chemistry variables, ranging from nutrients to relatively conservative ions, to better understand the roles of biogeochemical reactivity and solubility on connections between LULC and aquatic ecosystem response. Our study illustrates how different areas can have long groundwater pathways that represent different LULC than what can be seen on the landscape today. These groundwater pathways delay the arrival of nutrients and other water quality constituents, thus creating a legacy of historic land uses that eventually reaches surface water. We find that: 1) several water chemistry variables are best fit by legacy LULC while others have a stronger link to current LULC, and 2) single spatial scales of LULC analysis performed worse for most variables. Our novel combination of temporal and spatial scales was the best overall model fit for most variables, including SRP where this model explained 54% of the variation. We show that it is important to explicitly account for temporal and spatial context when linking LULC to ecosystem response.

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Martin et al. 2017.pdf

 

 

Yang, W., D. W. Hyndman, J. A. Winkler, A. Viña, J. Deines, F. Lupi, L. Luo, Y. Li, B. Basso, C. Zheng, D. Ma, S. Li, X. Liu, H. Zheng, G. Cao, Q. Meng, Z. Ouyang, and J. Liu. 2016. Urban water sustainability: framework and application. Ecology and Society 21(4):4. DOI:10.5751/ES-08685-210404

Abstract

Urban areas such as megacities (those with populations greater than 10 million) are hotspots of global water use and thus face intense water management challenges. Urban areas are influenced by local interactions between human and natural systems and interact with distant systems through flows of water, food, energy, people, information, and capital. However, analyses of water sustainability and the management of water flows in urban areas are often fragmented. There is a strong need to apply integrated frameworks to systematically analyze urban water dynamics and factors that influence these dynamics. We apply the framework of telecoupling (socioeconomic and environmental interactions over distances) to analyze urban water issues, using Beijing as a demonstration megacity. Beijing exemplifies the global water sustainability challenge for urban settings. Like many other cities, Beijing has experienced drastic reductions in quantity and quality of both surface water and groundwater over the past several decades; it relies on the import of real and virtual water from sending systems to meet its demand for clean water, and releases polluted water to other systems (spillover systems). The integrative framework we present demonstrates the importance of considering socioeconomic and environmental interactions across telecoupled human and natural systems, which include not only Beijing (the water-receiving system) but also water-sending systems and spillover systems. This framework helps integrate important components of local and distant human–nature interactions and incorporates a wide range of local couplings and telecouplings that affect water dynamics, which in turn generate significant socioeconomic and environmental consequences, including feedback effects. The application of the framework to Beijing reveals many research gaps and management needs. We also provide a foundation to apply the telecoupling framework to better understand and manage water sustainability in other cities around the world.

 

Pei L, Moore N, Zhong S, Kendall AD, Hyndman DW, et al. (2016) Effects of irrigation on the summer climate over the United States. J Clim 29: 3541–3558. doi:10.1175/JCLI-D-15-0337.1.

Abstract

Irrigation’s effects on precipitation during an exceptionally dry summer (June–August 2012) in the United States were quantified by incorporating a novel dynamic irrigation scheme into the Weather Research and Forecasting (WRF) Model. The scheme is designed to represent a typical application strategy for farmlands across the conterminous United States (CONUS) and a satellite-derived irrigation map was incorporated into the WRF-Noah-Mosaic module to realistically trigger the irrigation. Results show that this new irrigation approach can dynamically generate irrigation water amounts that are in close agreement with the actual irrigation water amounts across the high plains (HP), where the prescribed scheme best matches real-world irrigation practices. Surface energy and water budgets have been substantially altered by irrigation, leading to modified large-scale atmospheric circulations. In the studied dry summer, irrigation was found to strengthen the dominant interior high pressure system over the southern and central United States and deepen the trough over the upper Midwest. For the HP and central United States, the rainfall amount is slightly reduced over irrigated areas, likely as a result of a reduction in both local convection and large-scale moisture convergence resulting from interactions and feedbacks between the land surface and atmosphere. In areas downwind of heavily irrigated regions, precipitation is enhanced, resulting in a 20%–100% reduction in the dry biases (relative to the observations) simulated over a large portion of the downwind areas without irrigation in the model. The introduction of irrigation reduces the overall mean biases and root-mean-square errors in the simulated daily precipitation over the CONUS.

Article

Pei L, Moore N, Zhong S, Kendall AD, Hyndman DW, et al.2016.pdf

 

Deines, J.M., Liu, X., and Liu, J. 2016. Telecoupling in urban water systems: an examination of Beijing’s imported water supply. Water International 40:251-270. doi: 10.1080/02508060.2015.1113485

Abstract

A large imbalance between recharge and water withdrawal has caused vital regions of the High Plains Aquifer (HPA) to experience significant declines in storage. A new predevelopment map coupled with a synthesis of annual water levels demonstrates that aquifer storage has declined by approximately 410 km3 since the 1930s, a 15% larger decline than previous estimates. If current rates of decline continue, much of the Southern High Plains and parts of the Central High Plains will have insufficient water for irrigation within the next 20 to 30 years, whereas most of the Northern High Plains will experience little change in storage. In the western parts of the Central and northern part of the Southern High Plains, saturated thickness has locally declined by more than 50%, and is currently declining at rates of 10% to 20% of initial thickness per decade. The most agriculturally productive portions of the High Plains will not support irrigated production within a matter of decades without significant changes in management.

 

Article

Deines, J.M., Liu, X., and Liu, J. 2016.pdf

 

 

Smidt SJ, Haacker EMK, Kendall AD, Deines JM, Pei L, et al. (2016) Complex water management in modern agriculture: Trends in the water energy-food nexus over the High Plains Aquifer. Agric Water Manag 566-567: 988–1001. doi:10.1017/CBO9781107415324.004

Abstract

In modern agriculture, the interplay between complex physical, agricultural, and socioeconomic water use drivers must be fully understood to successfully manage water supplies on extended timescales. This is particularly evident across large portions of the High Plains Aquifer where groundwater levels have declined at unsustainable rates despite improvements in both the efficiency of water use and water productivity in agricultural practices. Improved technology and land use practices have not mitigated groundwater level declines, thus water management strategies must adapt accordingly or risk further resource loss. In this study, we analyze the water-energy-food nexus over the High Plains Aquifer as a framework to isolate the major drivers that have shaped the history, and will direct the future, of water use in modern agriculture. Based on this analysis, we conclude that future water management strategies can benefit from: (1) prioritizing farmer profit to encourage decision-making that aligns with strategic objectives, (2) management of water as both an input into the water-energy-food nexus and a key incentive for farmers, (3) adaptive frameworks that allow for short-term objectives within long-term goals, (4) innovative strategies that fit within restrictive political frameworks, (5) reduced production risks to aid farmer decision-making, and (6) increasing the political desire to conserve valuable water resources. This research sets the foundation to address water management as a function of complex decision-making trends linked to the water-energy-food nexus. Water management strategy recommendations are made based on the objective of balancing farmer profit and conserving water resources to ensure future agricultural production.

Article

Smidt SJ, Haacker EMK, Kendall AD, Deines JM, Pei L, et al.2016.pdf

 

Basso, B., Hyndman, D.W., Kendall, A.D., Grace, P.R., and Robertson, G.P., 2015, Can Impacts of Climate Change and Agricultural Adaptation Strategies Be Accurately Quantified if Crop Models Are Annually Re-Initialized? PLoS ONE 10(6): e0127333, doi:10.1371/journal.pone.0127333

Abstract

Estimates of climate change impacts on global food production are generally based on statistical or process-based models. Process-based models can provide robust predictions of agricultural yield responses to changing climate and management. However, applications of these models often suffer from bias due to the common practice of re-initializing soil conditions to the same state for each year of the forecast period. If simulations neglect to include year-to-year changes in initial soil conditions and water content related to agronomic management, adaptation and mitigation strategies designed to maintain stable yields under climate change cannot be properly evaluated. We apply a process-based crop system model that avoids re-initialization bias to demonstrate the importance of simulating both year-to-year and cumulative changes in pre-season soil carbon, nutrient, and water availability. Results are contrasted with simulations using annual re-initialization, and differences are striking. We then demonstrate the potential for the most likely adaptation strategy to offset climate change impacts on yields using continuous simulations through the end of the 21st century. Simulations that annually re-initialize pre-season soil carbon and water contents introduce an inappropriate yield bias that obscures the potential for agricultural management to ameliorate the deleterious effects of rising temperatures and greater rainfall variability.

Article

Basso, B., Hyndman, D.W.,  Kendall, A.D.,  Grace, P.R., and  Robertson, G.P., 2015.pdf

Verhougstraete M.P., Martin S.L., Kendall A.D., Hyndman D.W., and Rose J.B. 2015, Linking Fecal Bacteria in Rivers to Landscape, Geochemical, Hydrologic Factors, and Sources at the Basin Scale, Proceedings of the National Academy of Sciences (PNAS).

Abstract

Linking fecal indicator bacteria concentrations in large mixed-use watersheds back to diffuse human sources, such as septic systems, has met limited success. In this study, 64 rivers that drain 84% of Michigan’s Lower Peninsula were sampled under baseflow conditions for Escherichia coli, Bacteroides thetaiotaomicron (a human source-tracking marker), landscape characteristics, and geochemical and hydrologic variables. E. coli and B. thetaiotaomicron were routinely detected in sampled rivers and an E. colireference level was defined (1.4 log10 most probable number⋅100 mL−1). Using classification and regression tree analysis and demographic estimates of wastewater treatments per watershed, septic systems seem to be the primary driver of fecal bacteria levels. In particular, watersheds with more than 1,621 septic systems exhibited significantly higher concentrations of B. thetaiotaomicron. This information is vital for evaluating water quality and health implications, determining the impacts of septic systems on watersheds, and improving management decisions for locating, constructing, and maintaining on-site wastewater treatment systems.

Article

Verhougstraete M.P., Martin S.L., Kendall A.D., Hyndman D.W., and Rose J.B. 2015.pdf

Luscz, E., Kendall, A.D., and Hyndman, D.W.2015, High resolution spatially explicit nutrient source model for the lower peninsula of Michigan, Journal of Great Lakes Research 41(2)

Abstract

Nutrient loading to aquatic systems has been linked to many issues including eutrophication, harmful algal blooms, and decreases in species diversity. In the Great Lakes, algal blooms continue to plague Lake Erie and Saginaw Bay despite reductions in point source loading. Here, methods for predicting nutrient sources using GIS are described to examine the link between watershed nutrient sources, landscape processes, and in-stream loads in the Lower Peninsula of Michigan. These models predict all significant nutrient sources to the landscape at 30 m resolution over a 144,000 km2 region, avoiding the tradeoff between scale and source detail common to many existing watershed nutrient models. The model results presented here indicate that there is a high degree of variability in nutrient landscape loading rates, even within the same land use class. Within all land use types, except unmanaged lands, loading rates for most major sources varied by at least an order of magnitude. This work provides valuable information that can be used by environmental managers regarding how and where to target efforts to reduce nutrient loads in surface water particularly in the Great Lakes region where management efforts have been ongoing since the 1960s.

Article

Luscz, E., Kendall, A.D., and Hyndman, D.W.2015.pdf

Martin SL, Jasinski BL, Kendall AD, Dahl TA, Hyndman DW (2015) Quantifying beaver dam dynamics and sediment retention using aerial imagery, habitat characteristics, and economic drivers. Landsc Ecol 30: 1129–1144. doi: 10.1007/s10980-015-0165-9.

Abstract

Context: The North American beaver (Castor canadensis) population experienced a precipitous decline in the early twentieth century, fueled by the economic value of their pelts and habitat loss from forestry and agricultural expansion. The historical response of beaver populations to changing stresses is difficult to quantify due to a lack of population data. Objective: Here we characterize beaver dam dynamics as a surrogate measure for population and analyze spatio-temporal relationships with landscape and management characteristics, and estimate the potential of watershed beaver dam activity to sequester sediment. Methods: We use aerial photos from >70 years along with GIS analysis to quantify counts, sizes, and distributions of beaver dams and impoundments over time, including site recurrence. Human predation pressure and young aspen area are used to predictively model temporal changes in dam count. Finally, we estimate sediment retention through time by applying our data to published relationships. Results: Our analyses reveal a remarkable correlation between watershed beaver dam dynamics and statewide records of beaver harvest. Beaver dams show a pattern of spatial clustering as the number of dams increased, mostly in tributaries directly connected to the main river, regardless of stream order. Our multiple linear regression model predicts dam counts from pelt prices and young aspen area, producing an excellent fit (R2 = 0.86). Conclusions: We found evidence for beaver population recovery from near extirpation using relatively simple and widely-available measures. Methods we present can be used to estimate regional beaver population dynamics in other watersheds.

Article

Martin, SL, Jasinski, BL, Kendall, AD, Dahl,TA, Hyndman, DW,2015.pdf