Tara J. Troy

Debates—Perspectives on socio‐hydrology: Socio‐hydrologic modeling: Tradeoffs, hypothesis testing, and validation

Socio-hydrology focuses on studying the dynamics and co-evolution of coupled human and water systems. Recently, several new socio-hydrologic models have been published that explore these dynamics, and these models offer unique opportunities to better understand these coupled systems and to understand how water problems evolve similarly in different regions. These models also offer challenges, as decisions need to be made by the modeler on trade-offs between generality, precision, and realism. In addition, traditional hydrologic model validation techniques, such as evaluating simulated streamflow, are insufficient, and new techniques must be developed. As socio-hydrology progresses, these models offer a robust, invaluable tool to test hypotheses about the relationships between aspects of coupled human-water systems. They will allow us to explore multiple working hypotheses to greatly expand insights and understanding of coupled socio-hydrologic systems.

Virtual groundwater transfers from overexploited aquifers in the United States

Significance Irrigated agriculture is contributing to the depletion of the Central Valley, High Plains, and Mississippi Embayment aquifer systems. Agricultural production within these aquifer regions comprises a significant portion of the domestic and international cereal supply; thus, potential food security implications arise if production significantly decreases to bring groundwater withdrawals within sustainable limits. For the first time to our knowledge, this study tracks and quantifies the food and embodied groundwater resources from these aquifer systems to their final destination and determines the major US cities, US states, and countries that are currently most reliant upon them. Tracing virtual groundwater transfers highlights the role of distant demands on local groundwater sustainability and the fact that aquifer depletion must be considered within its global context. The High Plains, Mississippi Embayment, and Central Valley aquifer systems within the United States are currently being overexploited for irrigation water supplies. The unsustainable use of groundwater resources in all three aquifer systems intensified from 2000 to 2008, making it imperative that we understand the consumptive processes and forces of demand that are driving their depletion. To this end, we quantify and track agricultural virtual groundwater transfers from these overexploited aquifer systems to their final destination. Specifically, we determine which US metropolitan areas, US states, and international export destinations are currently the largest consumers of these critical aquifers. We draw upon US government data on agricultural production, irrigation, and domestic food flows, as well as modeled estimates of agricultural virtual water contents to quantify domestic transfers. Additionally, we use US port-level trade data to trace international exports from these aquifers. In 2007, virtual groundwater transfers from the High Plains, Mississippi Embayment, and Central Valley aquifer systems totaled 17.93 km3, 9.18 km3, and 6.81 km3, respectively, which is comparable to the capacity of Lake Mead (35.7 km3), the largest surface reservoir in the United States. The vast majority (91%) of virtual groundwater transfers remains within the United States. Importantly, the cereals produced by these overexploited aquifers are critical to US food security (contributing 18.5% to domestic cereal supply). Notably, Japan relies upon cereals produced by these overexploited aquifers for 9.2% of its domestic cereal supply. These results highlight the need to understand the teleconnections between distant food demands and local agricultural water use.

Dataset of 100-year flood susceptibility maps for the continental U.S. derived with a geomorphic method

Efficient strategies for preparing communities to protect against, respond to, recover from, and mitigate flood hazard are often hampered by the lack of information about the position and extent of flood-prone areas. Hydrologic and hydraulic analyses allow to obtain detailed flood hazard maps, but are a computationally intensive exercise requiring a significant amount of input data, which are rarely available both in developing and developed countries. As a consequence, even in data-rich environments, official flood hazard graduations are often affected by extensive gaps. In the U.S., for instance, the detailed floodplain delineation produced by the Federal Emergency Management Agency (FEMA) is incomplete, with many counties having no floodplain mapping at all. In this article we present a mapping dataset containing 100-year flood susceptibility maps for the continental U.S. with a 90 m resolution. They have been obtained performing a linear binary classification based on the Geomorphic Flood Index (GFI). To the best knowledge of the authors, there are no available flood-prone areas maps for the entire continental U.S. with resolution lower that 30׳׳×30׳׳ (approximatively 1 km at the equator).

The Use of DEM-Based Approaches to Derive a Priori Information on Flood-Prone Areas

Knowing the location and the extent of areas exposed to floods is the most basic information needed for planning flood management strategies. Unfortunately, a complete identification of these areas is still lacking in many countries. Recent studies have highlighted that a significant amount of information regarding the inundation process is already contained in the structure and morphology of a river basin. Therefore, several geomorphic approaches have been proposed for the delineation of areas exposed to flood inundation using DEMs. Such DEM-based approaches represent a useful tool, characterized by low cost and simple data requirements, for a preliminary identification of the flood-prone areas or to extend flood hazard mapping over large areas. Moreover, geomorphic information may be used as external constraint in remote-sensing algorithms for the identification of inundated areas during or after a flood event.

The U.S. food–energy–water system: A blueprint to fill the mesoscale gap for science and decision-making

Food, energy, and water (FEW) are interdependent and must be examined as a coupled natural–human system. This perspective essay defines FEW systems and outlines key findings about them as a blueprint for future models to satisfy six key objectives. The first three focus on linking the FEW production and consumption to impacts on Earth cycles in a spatially specific manner in order to diagnose problems and identify potential solutions. The second three focus on describing the evolution of FEW systems to identify risks, thus empowering the FEW actors to better achieve the goals of resilience and sustainability. Four key findings about the FEW systems that guide future model development are (1) that they engage ecological, carbon, water, and nutrient cycles most powerfully among all human systems; (2) that they operate primarily at a mesoscale best captured by counties, districts, and cities; (3) that cities are hubs within the FEW system; and (4) that the FEW system forms a complex network.