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Drought is an inescapable reality in many regions, including much of the western United States. With climate change, droughts are predicted to intensify and occur more frequently, making the imperative for drought management even greater. Many diverse actors – including private landowners, business owners, scientists, non-governmental organizations (NGOs), and managers and policymakers within tribal, local, state, and federal government agencies – play multiple, often overlapping roles in preparing for and responding to drought. Managing water is, of course, one of the most important roles that humans play in both mitigating and responding to droughts; but, focusing only on “water managers” or “water management”...
Categories: Publication; Types: Citation
The impacts of the United States drought of 2007 to both society and ecosystems were substantive and included multi-billion dollar agricultural losses and the second worst wildfire season on record. The purpose of this paper is to place the 2007 drought in historical perspective relative to the climate record from 1895?2007 to increase our understanding of this hazard and contribute to improvements of drought mitigation plans. We compared the 2007 drought historically against the climatic record (1895?2007) using the Palmer Drought Severity Index (PDSI). We then examined the temporal progression of the 2007 drought and placed the peak month of drought severity (November) in historical perspective using rankings...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12847/full): Climate models predict increasing drought intensity and frequency for many regions, which may have negative consequences for tree recruitment, growth and mortality, as well as forest ecosystem services. Furthermore, practical strategies for minimizing vulnerability to drought are limited. Tree population density, a metric of tree abundance in a given area, is a primary driver of competitive intensity among trees, which influences tree growth and mortality. Manipulating tree population density may be a mechanism for moderating drought-induced stress and growth reductions, although the relationship between tree population density and...
Frequent and persistent droughts exacerbate the problems caused by the inherent scarcity of water in the semiarid to arid parts of the southwestern United States. The occurrence of drought is driven by climatic variability, which for years before about the beginning of the 20th century in the Southwest must be inferred from proxy records. As part of a multidisciplinary study of the potential hydrologic impact of severe sustained drought on the Colorado River, the physical basis and limitations of tree rings as indicators of severe sustained drought are reviewed, and tree-ring data are analyzed to delineate a “worst-case� drought scenario for the Upper Colorado River Basin (UCRB). Runs analysis of a 121-site...
This 2-pager describes the Evaporative Demand Drought Index (EDDI), which is a drought index that can serve as an indicator of both rapidly evolving “flash” droughts (developing over a few weeks) and sustained droughts (developing over months but lasting up to years).
The future of dry forests around the world is uncertain given predictions that rising temperatures and enhanced aridity will increase drought-induced tree mortality. Using forest management and ecological restoration to reduce density and competition for water offers one of the few pathways that forests managers can potentially minimize drought-induced tree mortality. Competition for water during drought leads to elevated tree mortality in dense stands, although the influence of density on heat-induced stress and the durations of hot or dry conditions that most impact mortality remain unclear. Understanding how competition interacts with hot-drought stress is essential to recognize how, where and how much reducing...
Categories: Publication; Types: Citation
Severe droughts have been associated with regional-scale forest mortality worldwide. Climate change is expected to exacerbate regional mortality events; however, prediction remains difficult because the physiological mechanisms underlying drought survival and mortality are poorly understood. We developed a hydraulically based theory considering carbon balance and insect resistance that allowed development and examination of hypotheses regarding survival and mortality. Multiple mechanisms may cause mortality during drought. A common mechanism for plants with isohydric regulation of water status results from avoidance of drought-induced hydraulic failure via stomatal closure, resulting in carbon starvation and a cascade...
In response to recent severe drought conditions throughout the state, Arizona recently developed its first drought plan. The Governor's Drought Task Force focused on limiting the economic and social impacts of future droughts through enhanced adaptation and mitigation efforts. The plan was designed to maximize the use of new, scientific breakthroughs in climate monitoring and prediction and in vulnerability assessment. The long term objective of the monitoring system is to allow for evaluation of conditions in multiple sectors and at multiple scales. Stakeholder engagement and decision support are key objectives in reducing Arizona's vulnerability in light of the potential for severe, sustained drought. The drivers...
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The South Central U.S. is one of the main agricultural regions in North America: annual agricultural production is valued at more than $44 billion dollars. However, as climate conditions change, the region is experiencing more frequent and severe droughts, with significant impacts on agriculture and broader consequences for land management. For example, in 2011 drought caused an estimated $7.6 billion in agricultural losses in Texas and an additional $1.6 billion in Oklahoma. Although there are many drought monitoring tools available, most of these tools were developed without input from the stakeholders, such as farmers and ranchers, who are intended to use them. The goal of this project is to assess the information...
Economic, environmental, and societal impacts of drought are severe and extremely costly. For 1988 alone, the Climate Prediction Center calculated that drought cost the US$39 billion (in 1988 dollars). Vulnerability to drought?a routinely occurring part of the natural hydrologic cycle?is increasing in all parts of the United States due to: population growth and population shifts, especially in the water-short western states and in the Southeast; land-use changes; global climate change; and increased water resource demands. The U.S. population has increased by about 50% since 1970 to more than 300 million, much of that occurring in water-scarce western regions. Land use changes due to development and other activities...
Categories: Publication; Types: Citation
Abstract (from AGU100): Forest conservation and carbon sequestration efforts are on the rise, yet the long‐term stability of these efforts under a changing climate remains unknown. We generate nearly three decades of remotely sensed canopy water content throughout California, which we use to determine patterns of drought stress. Linking these patterns of drought stress with meteorological variables enables us to quantify spatially explicit biophysical drought resistance in terms of magnitude and duration. These maps reveal significant spatial heterogeneity in drought resistance and demonstrate that almost all forests have less resistance to severe, persistent droughts. By identifying the spatial patterning of biophysical...
A critical aspects of the uniqueness of coastal drought is the effects on salinity dynamics of creeks and rivers. The location of the freshwater-saltwater interface along the coast is an important factor in the ecological and socio-economic dynamics of coastal communities. Salinity is a critical response variable that integrates hydrologic and coastal dynamics including streamflow, precipitation, sea level, tidal cycles, winds, and tropical storms. The position of the interface determines the composition of freshwater and saltwater aquatic communities as well as the freshwater availability for water intakes. Many definitions of drought have been proposed, with most describing a decline in precipitation which has...
Southern California relies heavily upon imported water from the Sacramento and Colorado river systems to augment local supplies and to mitigate the impacts of drought. In this paper a ‘perfect drought’ is defined as a prolonged drought that affects southern California, the Sacramento River basin and the upper Colorado River basin simultaneously. Examination of instrumental climate and discharge records shows that over the past century such perfect droughts do occur, but generally persist for less than five years. Perfect droughts that extend across all three areas are associated with anomalous upper-level high pressure off west coast and over western North America which is in turn associated with anomalously...
New tree-ring records of ring-width from remnant preserved wood are analyzed to extend the record of reconstructed annual flows of the Colorado River at Lee Ferry into the Medieval Climate Anomaly, when epic droughts are hypothesized from other paleoclimatic evidence to have affected various parts of western North America. The most extreme low-frequency feature of the new reconstruction, covering A. D. 762-2005, is a hydrologic drought in the mid-1100s. The drought is characterized by a decrease of more than 15% in mean annual flow averaged over 25 years, and by the absence of high annual flows over a longer period of about six decades. The drought is consistent in timing with dry conditions inferred from tree-ring...
THE RISING RISK OF DROUGHT. Droughts of the twenty-first century are characterized by hotter temperatures, longer duration, and greater spatial extent, and are increasingly exacerbated by human demands for water. This situation increases the vulnerability of ecosystems to drought, including a rise in drought-driven tree mortality globally (Allen et al. 2015) and anticipated ecosystem transformations from one state to another—for example, forest to a shrubland (Jiang et al. 2013). When a drought drives changes within ecosystems, there can be a ripple effect through human communities that depend on those ecosystems for critical goods and services (Millar and Stephenson 2015). For example, the “Millennium Drought”...
Categories: Publication; Types: Citation
Ongoing drought in the Colorado River Basin, unprecedented urban growth in the watershed, and numerical model simulations showing higher temperatures and lower precipitation totals in the future have all combined to heighten interest in drought in this region. In this investigation, we use principal components analysis (PCA) to independently assess the influence of various teleconnections on Basin-wide and sub-regional winter season Palmer Hydrological Drought Index (PHDI) and precipitation variations in the Basin. We find that the Pacific Decadal Oscillation (PDO) explains more variance in PHDI than El Nio-Southern Oscillation (ENSO), the Atlantic Multidecadal Oscillation (AMO), and the planetary temperature combined...
The waters of the Colorado River are divided among seven states according to a complex ?Law of the River? drawn from interstate compacts, international treaties, statutes, and regulations. The Law of the River creates certain priorities among the states and the Republic of Mexico, and in the event of a severe sustained drought, the Law of the River dictates the distribution of water and operation of the elaborate reservoir system. Earlier work indicated that there is remarkable resilience in the system for established uses of water in the Lower Basin of the Colorado River. This work shows, based on an application of the Law of the River using computer modeling of operations of facilities on the Colorado River, that...
Hidalgo, H.G., Dettinger, M.D., and Cayan, D.C., 2008, Changes in Aridity in the Western United States: Californa Drought: An Update -- 2008, California Department of Water Resources, State of California, p. 54-59. (on-line report in pdf format, 4148 KB)
Categories: Publication; Types: Citation
Abstract (from Ecosphere): When animals select areas to occupy, decisions involve trade‐offs between the fitness benefits of obtaining critical resources and minimizing costs of biotic and abiotic factors that constrain their use. These processes can be more dynamic and complex for species inhabiting desert environments, where highly variable spatial and temporal distribution of precipitation can create high intra‐ and inter‐annual variability in forage conditions and water availability, and thermal constraints can differ significantly among seasons and diel periods. We examined resource selection in desert bighorn sheep (Ovis canadensis mexicana) in Cabeza Prieta National Wildlife Refuge, Arizona, USA, at multiple...
Categories: Publication; Types: Citation
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Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. They are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. These general purpose regions are critical for structuring and implementing ecosystem management strategies across federal agencies, state agencies, and nongovernment organizations that are responsible for different types of resources within the same geographical areas. The approach used to compile this map is based on the premise that ecological regions can be identified through the analysis of patterns of biotic and abiotic phenomena, including...
map background search result map search result map Southwest Energy Development and Drought Drought Indicators of the South Central Plains (1981-2014) Southwest Energy Development and Drought Drought Indicators of the South Central Plains (1981-2014)