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.

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.

Article

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

Haacker EMK, Kendall AD, Hyndman DW (2015) Water Level Declines in the High Plains Aquifer: Predevelopment to Resource Senescence. Ground Water 54: 231–242. doi:10.1111/gwat.12350

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

Haacker EMK, Kendall AD, Hyndman DW 2015.pdf

 

Cullin, J.A., Endreny, T.A., Lautz, L.K., Robinson, J., Smidt, S.J., Ward, A.S., Zimmer, M.A. 2014. A comparison of hyporheic transport at a cross-vane structure and natural riffle. Groundwater.

Abstract

While restoring hyporheic flowpaths has been cited as a benefit to stream restoration structures, little documentation exists confirming that constructed restoration structures induce comparable hyporheic exchange to natural stream features. This study compares a stream restoration structure (cross- vane) to a natural feature (riffle) concurrently in the same stream reach using time lapsed electrical resistivity (ER) tomography. Using this hydrogeophysical approach, we were able to quantify hyporheic extent and transport beneath the cross -vane structure and riffle. We interpret from the geophysical data that th e cross-vane and natural riffle induced spatially and temporally unique hyporhei c extent and transport, and the cross-vane created both spatially larger and temporally longer hyporheic flowpaths than the natural riffle.Tracer from the 4.67-hr injection was detected along flowpaths for 4.6-hrs at the cross- vane and 4.2-hrs at the riffle. The spatial extent of the hyporheic zone at the cross-vane was 12% larger than at the riffle. We compare ER results of this study to vertical fluxes calculated from temperature profiles and conclude significant differences in the interpretation of hyporheic transport from these different field techniques. Results of this study demonstrate a high degree of heterogeneity in transport metrics at both the cross-vane and riffle and differences between the hyporheic flowpath networks at the two different features. Our results suggest that restoration structures may be capable of creating sufficient exchange flux and timescales of transport to achieve the same ecological functions as natural features, but engineering of the physical and biogeochemical environment may be necessary to realize those benefits.

Article

Cullin, J.A., Endreny, T.A., Lautz, L.K., Robinson, J., Smidt, S.J., Ward, A.S., Zimmer, M.A. 2014.pdf

 

Hyndman, D.W. 2014. Impacts of Projected Changes in Climate on Hydrology. Bill Freedman (ed.), Handbook of Global Environmental Change, Springer. doi:10.1007/978-94-007-5784-4_131.

Abstract:

Global temperatures are projected to rise by several degrees C over the next century, with more dramatic warming over land masses; precipitation is expected to become more variable with increases in polar regions and decreases in mid-latitude areas. Such changes in climate will have major impacts on hydrology, with more flooding expected in humid regions and more droughts in arid areas. Warming is also causing rapid shrinking of glaciers and decline of snowpack that are important to water supplies around the world. Such climate changes are likely to cause additional stress on water resources in many areas of the world at the same time demands are expected to increase due to population growth.

Article:

Hyndman, D.W. 2014. Impacts of Projected Changes in Climate on Hydrology.pdf

Van Dam, R.L., Eustice, B., Hyndman, D.W., Wood, W.W., Simmons, C.T. 2014. Electrical Imaging and Fluid Modeling of Transient Free Convection in a Shallow Water-Table Aquifer. Water Resources Research, 50. doi:10.1002/2013WR013673.

Abstract:

Unstable density-driven flow can lead to enhanced solute transport in groundwater. Only recently has the complex fingering pattern associated with free convection been documented in field settings. Electrical resistivity (ER) tomography has been used to capture a snapshot of convective instabilities at a single point in time, but a thorough transient analysis is still lacking in the literature. We present the results of a 2 year experimental study at a shallow aquifer in the United Arab Emirates that was designed to specifically explore the transient nature of free convection. ER tomography data documented the presence of convective fingers following a significant rainfall event. We demonstrate that the complex fingering pattern had completely disappeared a year after the rainfall event. The observation is supported by an analysis of the aquifer halite budget and hydrodynamic modeling of the transient character of the fingering instabilities. Modeling results show that the transient dynamics of the gravitational instabilities (their initial development, infiltration into the underlying lower-density groundwater, and subsequent decay) are in agreement with the timing observed in the time-lapse ER measurements. All experimental observations and modeling results are consistent with the hypothesis that a dense brine that infiltrated into the aquifer from a surficial source was the cause of free convection at this site, and that the finite nature of the dense brine source and dispersive mixing led to the decay of instabilities with time. This study highlights the importance of the transience of free convection phenomena and suggests that these processes are more rapid than was previously understood.

Article:

Van Dam, R.L., Eustice, B., Hyndman, D.W., Wood, W.W., Simmons, C.T. 2014.pdf

Pei, L., Moore, N., Zhong, S.S., Luo, L., Hyndman, D.W., Heilman, W.E., Gao, Z. 2014. WRF Model Sensitivity to Land Surface Scheme and Cumulus Parameterization under Short-term Climate Extremes over the Southern Great Plains of the United States. Journal of Climate. doi:10.1175/JCLI-D-14-00015.1.

Abstract:

Extreme weather and climate events, especially short-term excessive drought and we periods over agricultural areas, have received increased attention. The Southern Great Plains (SGP) is one of the largest agricultural regions in North America and features the underlying Ogallala-High Plains Aquifer system worth great economic value due in large part to production gains from groundwater. Climate research over the SGP is needed to better understand complex coupled climate-hydrology-socioeconomic interactions critical to the sustainability of this region, especially under extreme climate scenarios. Here we studied growing-season extreme conditions using the Weather Research and Forecasting model(WRF). The six most extreme recent years, both wet and dry, were simulated to investigate the impacts of land-surface model and cumulus parameterization on the simulated hydroclimate. The results show that under short-term climate extremes, the land-surface model plays a more important role modulating the land-atmosphere water budget, and thus the entire regional climate, than the cumulus parameterization under current model configurations. Between the two land-surface models tested, the more sophisticated land -surface model produced significantly larger wet bias due in large part to overestimation of moisture flux convergence, which is attributed mainly to an overestimation of the surface evapotranspiration during the simulated period. The deficiencies of the cumulus parameterizations resulted in the model’s inability to depict the diurnal rainfall variability. Both land-surface processes and cumulus parameterizations remain the most challenging parts of regional climate modeling under extreme climates over the SGP, with the former strongly affecting the precipitation amount and the latter strongly affecting the precipitation pattern.

Article:

Pei, Moore, Zhong, Luo, Hyndman, Heilman, Gao. 2014-in press.pdf

 

 

Brena, A., Kendall, A.D., D.W. Hyndman. 2014. Improved methods for Satellite-based Groundwater Storage Estimates: A Decade of Monitoring the High Plains Aquifer from Space and Ground Observations. Geophysical Research Letters 41, doi:10.1002/2014GL061213.

Abstract:

The impacts of climate extremes and water use on groundwater storage across large aquifers can be quantified using Gravity Recovery and Climate Experiment (GRACE) satellite monitoring. We present new methods to improve estimates of changes in groundwater storage by incorporating irrigation soil moisture corrections to common data assimilation products. These methods are demonstrated using data from the High Plains Aquifer (HPA) for 2003 to 2013. Accounting for the impacts of observed and inferred irrigation on soil moisture significantly improves estimates of groundwater storage changes as verified by interpolated measurements from ~10,000 HPA wells. The resulting estimates show persistent declines in groundwater storage across the HPA, more severe in the southern and central HPA than in the north. Groundwater levels declined by an average of approximately 276±23mm from 2003 to 2013, resulting in a storage loss of 125±4.3km3, based on the most accurate of the three methods developed here.

Article:

Brena-Naranjo, Kendall, Hyndman – 2014