Global water availability boosted by vegetation-driven changes in atmospheric moisture transport

Nature Portfolio (Springer Nature) | October 31st, 2022

Surface-water availability, defined as precipitation minus evapotranspiration, can be affected by changes in vegetation. These impacts can be local, due to the modificati

Surface-water availability, defined as precipitation minus evapotranspiration, can be affected by changes in vegetation. These impacts can be local, due to the modification of evapotranspiration and precipitation, or non-local, due to changes in atmospheric moisture transport. However, the teleconnections of vegetation changes on water availability in downwind regions remain poorly constrained by observations. By linking measurements of local precipitation to a new hydrologically weighted leaf area index that accounts for both local and upwind vegetation contributions, we demonstrate that vegetation changes have increased global water availability at a rate of 0.26 mm yr−2 for the 2001–2018 period. Critically, this increase has attenuated about 15% of the recently observed decline in global water availability. The water availability increase is due to a greater rise in precipitation relative to evapotranspiration for over 53% of the global land surface. We also quantify the potential hydrological impacts of regional vegetation increases at any given location across global land areas. We find that enhanced vegetation is beneficial to both local and downwind water availability for ~45% of the land surface, whereas it is adverse elsewhere, primarily in water-limited or high-elevation regions. Our results highlight the potential strong effects of deliberate vegetation changes, such as afforestation programmes, on water resources beyond local and regional scales.

Going Beyond Low Flows: Streamflow Drought Deficit and Duration Illuminate Distinct Spatiotemporal Drought Patterns and Trends in the U.S. During the Last Century

American Geophysical Union (AGU) | August 30th, 2022

Streamflow drought is a recurring challenge, and understanding spatiotemporal patterns of past droughts is needed to manage future water resources. We examined regional p

Streamflow drought is a recurring challenge, and understanding spatiotemporal patterns of past droughts is needed to manage future water resources. We examined regional patterns in streamflow drought metrics and compared these metrics to low flow timing and magnitude using long-term daily records for 555 minimally disturbed watersheds. For each streamgage, we calculated streamflow drought duration (number of days) and deficit (flow volume below a specified threshold) for each climate year (April 1–March 31). We identified drought using five thresholds (2%–30%) and two approaches: variable thresholds with unique values for each day of the year, and a fixed threshold based on all period-of-record flows. We then analyzed drought trends using the Mann-Kendall test with persistence adjustment for 1921–2020, 1951–2020, and 1981–2020, and computed correlations between annual streamflow drought metrics and climate metrics using values from a monthly water balance model. Spatial patterns in drought metrics were consistent between variable and fixed approaches, though fixed threshold durations were typically longer and variable threshold deficits larger. High interannual variability in drought duration emerged in the central, interior west, and southwestern U.S., with high deficit variability in the interior west. Drought metrics were weakly correlated with low flow magnitude and timing, providing unique information. Drought duration and deficit increased in the southern and western U.S. for both 1951–2020 and 1981–2020, particularly using fixed thresholds, and paralleled trends in aridity. Projections of continued aridification for the southern and western U.S. may increase drought durations and deficits and intensify water availability impacts.

Gone with the flow

Bay Institute | August 1st, 2010

The Bay Institute's primer Gone with the Flow describes in plain language how runoff flowing from the mountain watersheds ringing California’s Central Valley provided c

The Bay Institute's primer Gone with the Flow describes in plain language how runoff flowing from the mountain watersheds ringing California’s Central Valley provided coldwater paradises for salmon returning to their native streams; turned lowland rivers and their floodplains into a rich source of food and shelter for young fish; mingled in the Delta’s complex maze of marshes and sloughs; and created a vast expanse of brackish water habitat essential for estuarine creatures in the upper reaches of San Francisco Bay. The primer also explains how the lack of access to most upland streams now forces migratory fish to cope with undesirable, often lethal flow conditions; how runoff in lowland rivers has been shifted from spring to summer, or even almost completely cut off in the San Joaquin basin, with disastrous consequences for the environment; how reverse flows in Delta channels kill hundreds of millions of aquatic organisms each year; and how the Bay is now in a permanent ecological drought because of the diversion of half its freshwater inflow.

Goodbye to “Rough Fish”: Paradigm Shift in the Conservation of Native Fishes

American Fisheries Society (AFS) | July 21st, 2021

Goodbye to “Rough Fish”: Paradigm Shift in the Conservation of Native Fishes

American Fisheries Society (AFS) | July 21st, 2021

While sometimes difficult to admit, perspectives of European and white males have overwhelmingly dominated fisheries science and management in the USA. This dynamic is ex

While sometimes difficult to admit, perspectives of European and white males have overwhelmingly dominated fisheries science and management in the USA. This dynamic is exemplified by bias against “rough fish”—a pejorative ascribing low-to-zero value for countless native fishes. One product of this bias is that biologists have ironically worked against conservation of diverse fishes for over a century, and these problems persist today. Nearly all U.S. states retain bag limits and other policies that are regressive and encourage overfishing and decline of native species. Multiple lines of evidence point towards the need for a paradigm shift. These include: (1) native species deliver critical ecosystem services; (2) little demonstration that native fish removals deliver intended benefits; (3) many native fishes are long-lived and vulnerable to overfishing and decline; and (4) fisher values and demographics shifting towards native fish conservation. Overall, existing native fish policies are unacceptable and run counter to the public trust doctrine where government agencies manage natural resources for public use. We encourage agencies to revisit their policies regarding native fishes and provide suggestions for developing more holistic, protective, and inclusive conservation policy.

Governing Nature: Bambi Law in a Wall-E World

Social Science Research Network (SSRN) | January 28th, 2021

Humanity has disrupted many of the fundamental processes that shape nature worldwide. Virtually no places remain unchanged. Many ecosystems have moved far from their hist

Humanity has disrupted many of the fundamental processes that shape nature worldwide. Virtually no places remain unchanged. Many ecosystems have moved far from their historic conditions and no longer support native species or traditional human uses. In the Anthropocene, a new geologic era dominated by the human impact on Earth, these problems will continue to get worse. In response, humans are intervening in ecosystems at a massive scale. This Article argues that, even as humanity engages in an unprecedented level of ecosystem management, existing environmental governance structures are ill suited to manage this new nature. Ecologists who focus on restoring ecosystems have begun to abandon efforts to recreate idealized historical ecosystems, recognizing that such efforts will fail. Instead, they embrace new approaches that acknowledge continuing human impacts and seek to shape impacted habitats in a way that benefits both human and other life. This Article examines the new ecological approaches, using their migration of purpose and approach to illuminate ecosystem management in the Anthropocene and the new obligations it places on environmental law. To sharpen this focus, the Article considers three case studies of managed ecosystems, detailing the extent to which humans are controlling nature. The case studies suggest that the existing literature seriously underestimates the magnitude of the questions society will soon face. The Article concludes that although we face the daunting prospect of reshaping the very fabric of nature, we lack the governance structures to decide what shape it should take. Society will need environmental law governance that can answer fundamental questions about humanity’s role in managing nature at all scales. This Article proposes several starting principles to encourage legal scholars to address this need.

Grassland Groundwater Sustainability Agency Groundwater Sustainability Plan

Grassland Groundwater Sustainability Agency (GGSA) | January 17th, 2020

*Cover gives draft date of December but consulting engineer signature is for 1/17/2020

*Cover gives draft date of December but consulting engineer signature is for 1/17/2020

Ground-Water Conditions in Amargosa Desert, Nevada-California, 1952-87

U.S. Geological Survey (USGS) | July 1st, 1991

Groundwater Characterization and Effects of Pumping in the Death Valley Regional Groundwater Flow System, Nevada and California, with Special Reference to Devils Hole

U.S. Geological Survey (USGS) | March 5th, 2020

Groundwater flow and development were characterized in four groundwater basins of the Death Valley regional flow system in Nevada and California with calibrated, groundwa

Groundwater flow and development were characterized in four groundwater basins of the Death Valley regional flow system in Nevada and California with calibrated, groundwater-flow models. Natural groundwater discharges in the Furnace Creek, Lower Amargosa, and Saratoga Spring areas were defined and distributed consistently with a revised hydrogeologic framework. This simplified hydrogeologic framework was limited to four hydraulically unique, hydrogeologic units: (1) basin fill; (2) carbonate rocks; (3) volcanic rocks; and (4) low-permeability granitic and siliciclastic rocks. Hydrogeologic units and division of carbonate and volcanic rocks between shallow and deep were supported by results from 271 aquifer tests and specific-capacity estimates. Greater than 90 percent of field-estimated transmissivity occurred within 1,600 feet (ft) of the water table. Pumping in the study area from 1960 to 2010 averaged 46,000 acre-feet per year (acre-ft/yr), which is 80 percent of the predevelopment discharge. The central Amargosa Desert and Pahrump Valley were the two primary pumping centers and measurably affected water levels across 900 square miles in 2018. Water levels in Devils Hole were a special focus because endangered Devils Hole pupfish (Cyprinodon diabolis) are affected by water-level declines. Pumping 42,100 acre-ft by Cappaert Enterprises, formerly Spring Meadows, Inc., caused a 2.3-ft water-level decline in Devils Hole, which temporarily reduced habitat of Devils Hole pupfish by 85 percent in 1972. If no pumping occurred, water levels in Devils Hole would have risen naturally about 1 ft between 1973 and 2018 from temporal variations in recharge. The 2.6-ft range of measured water-level changes in Devils Hole was simulated with a root-mean-square error of 0.2 ft during the 70-year period of record. Simulated water-level declines from pumping totaled 1.4 ft in 2018, with 25 and 34 percent attributed to pumping by Cappaert Enterprises and the central Amargosa Desert, respectively. Water levels in Devils Hole will decline at rates of 0.1–0.2 ft per decade if pumping from Ash Meadows groundwater basin and the central Amargosa Desert continue at current rates. Effects of future natural water-level fluctuations remain unknown. Ash Meadows and Alkali Flat–Furnace Creek Ranch groundwater basins are hydraulically connected near well AD-4, about 5 miles south of the town of Amargosa Valley, Nevada. About 40 percent of the discharge from the Furnace Creek area is recharged in the Ash Meadows groundwater basin. Basin fill in the central Amargosa Desert hydraulically connects carbonate rocks east of well AD-4 with saturated carbonate rocks in the Funeral Range. About 7 percent of the 960,000 acre-ft pumped from Ash Meadows and Alkali Flat–Furnace Creek Ranch groundwater basins prior to 2019 was captured discharge from springs and phreatophytes. Greater than 40 percent of the 2,080,000 acre-ft pumped from Pahrump Valley between 1910 and 2019 was capture that primarily discharged from Bennetts and Manse Springs. Simulated advective-flow distances and velocities from underground nuclear tests are within the range of advective transport calculations from tritium data and previous radionuclide transport investigations. Boundary conditions and flow rates from the regional model in this study are plausible for local-scale flow and radionuclide transport models. Simulated 165-year groundwater-flow paths do not extend into pumping areas and effects of regional pumping on advective transport are negligible.

Groundwater Dependent Ecosystems under the Sustainable Groundwater Management Act

Nature Conservancy | February 1st, 2018

The Sustainable Groundwater Management Act (SGMA) of 2014 is landmark legislation in California that empowers local agencies, known as groundwater sustainability agencies

The Sustainable Groundwater Management Act (SGMA) of 2014 is landmark legislation in California that empowers local agencies, known as groundwater sustainability agencies (GSAs), to sustainably manage groundwater resources for current and future social, economic, and environmental benefits. In addition to balancing these multiple benefits, SGMA includes specific requirements to identify and consider impacts to groundwater dependent ecosystems (GDEs). Recognizing data and resource limitations, The Nature Conservancy developed this guidance document based on best available science to help agencies, consultants, and stakeholders efficiently incorporate GDEs into groundwater sustainability plans (GSPs). The Nature Conservancy’s tools and resources are intended to reduce costs, shorten timelines, and increase benefits for both people and nature.