Groundwater Dynamics in the Colorado River Limitrophe

Pacific Institute | May 23rd, 2013

The Colorado River, diverted and channelized and intensively managed, only rarely has enough water to flow even 20 miles past Morelos Dam, the last dam on the river, near

The Colorado River, diverted and channelized and intensively managed, only rarely has enough water to flow even 20 miles past Morelos Dam, the last dam on the river, near the California/Arizona/Baja California border. The river’s limitrophe reach – the roughly 22.5 mile stretch from Andrade to San Luis that separates Baja California from Arizona – is generally considered the uppermost extent of the remnant Colorado River delta, with some of the most extensive stands of native cottonwoods and willows left on the lower Colorado River and one of the few areas where the river still occasionally has enough water to exceed its banks and reach its floodplain. Because of this, there has been intense restoration interest in the limitrophe reach for more than a decade. In recent years, however, concern has grown that deteriorating groundwater conditions in the lower portion of the limitrophe will limit the success of restoration efforts. Groundwater Dynamics in the Colorado River Limitrophe describes and explains the changing groundwater conditions in and adjacent to the Colorado River’s limitrophe reach, and analyzes the impact of groundwater pumping on these overdraft conditions. The key question underlying this study asks how changing groundwater conditions in the limitrophe could affect the sustainability of planned habitat restoration projects. This study indicates that, even after the exceptionally dry period of 2005-2009, when surface flows failed to reach the gage at the downstream end of the limitrophe on 90 percent of days, more than a third of the channel through the limitrophe still exhibited connectivity with the water table, and roughly two-thirds of the limitrophe still had a water table that remained within the reach of the roots of cottonwoods and willows. The plunging water table at the downstream end of the limitrophe suggests that the final five miles of the river within the limitrophe may not respond to efforts to restore riparian habitat, at least not without a long-term commitment to supplemental irrigation, but areas upstream appear well-insulated from the recent drawdown and would benefit from restoration activity, such as that proposed by the recent Minute 319.

Groundwater Geology and Hydrology of Death Valley National Park, California and Nevada

U.S. Department of the Interior (DOI) | December 3rd, 2012

Guidelines for salmonid passage at stream crossings

National Marine Fisheries Service (NMFS) | August 20th, 2013

This document provides guidelines for design of stream crossings to aid upstream and downstream passage of migrating salmonids. It is intended to facilitate the design of

This document provides guidelines for design of stream crossings to aid upstream and downstream passage of migrating salmonids. It is intended to facilitate the design of a new generation of stream crossings, and assist the recovery of threatened and endangered salmon species. These guidelines are offered by the National Marine Fisheries Service, Southwest Region (NMFS-SWR), as a result of its responsibility to prescribe fishways under the Endangered Species Act, the Magnuson-Stevens Act, the Federal Power Act, and the Fish and Wildlife Coordination Act. The guidelines apply to all public and private roads, trails, and railroads within the range of anadromous salmonids in California.

Guidelines to NOAA Fisheries Staff for the Evaluation of Sediment Removal Actions from California Streams

National Marine Fisheries Service (NMFS) | April 19th, 2004

The National Marine Fisheries Service (NOAA Fisheries) is responsible for protecting, managing, and conserving marine, estuarine, and anadromous fish resources and their

The National Marine Fisheries Service (NOAA Fisheries) is responsible for protecting, managing, and conserving marine, estuarine, and anadromous fish resources and their habitats under various legal authorities (Appendix 1). A guidance document specific to the NOAA Fisheries Southwest Region (SWR) for instream sediment removal is appropriate, because such actions have the potential to adversely affect all life stages of listed salmonids and because sediment removal actions are widespread in California streams. The scientific literature documents that instream gravel mining operations and salmonids are often attracted to the same locations. The effects of instream gravel mining and channel maintenance have been widely recognized as potential impacts to aquatic resources. At least 13 states and 8 foreign countries have implemented restrictions or prohibitions on commercial sediment excavation from fish-bearing streams. Oregon and Washington have reallocated their aggregate  resource production from streams to predominantly floodplains and geologic deposits. Aggregate production in California is focused primarily on streams. The annual aggregate extraction in California is estimated to exceed natural replenishment by an order of magnitude. In California the demand for high-quality aggregate materials is high because of a rapidly growing population, expanding industry, and the geologic nature of the most populous areas. NOAA Fisheries anticipates that pressures for stream-derived aggregates will continue to increase in the SWR. This convergence of geology and accelerating market demand has significant implications for the conservation and recovery of the freshwater habitats entrusted to NOAA Fisheries.

Gut Contents Analysis of Four Fish Species Collected in the San Leandro Bay RMP PCB Study in August 2016

San Francisco Estuary Institute (SFEI) | November 7th, 2018

In support of PCB modeling for San Leandro Bay, a Priority Margin Unit (PMU) for PCB load reduction in the estuary, fish samples of four species (topsmelt, shiner perch,

In support of PCB modeling for San Leandro Bay, a Priority Margin Unit (PMU) for PCB load reduction in the estuary, fish samples of four species (topsmelt, shiner perch, white croaker, and northern anchovy ) were obtained in August 2016 for both tissue analysis and examination of gut contents. The bay was sampled at eight locations, with a repeated sampling at one location (Airport Lagoon) for one species (topsmelt). Fish were measured, weighed, and dissected, and their gut contents examined microscopically. Topsmelt (9 samples, 188 specimens) had the greatest variety of food items, with gammarid amphipods and chain diatoms predominating. Some topsmelt, especially larger individuals, consumed macroalgae as a major dietary component. Two samples at two sites for shiner perch (20 fish each) had contents composed of close to 50% gammarids at both sites, but differed in proportions of bivalves and polychaetes among the important food items. The one sample of white croaker had consumed mostly gammarids, with fish and polychaetes ranking next in importance. A single sample of northern anchovy (20 fish analyzed) differed radically from the other species in consuming mainly a diatom that appears to have been filtered from the water column. Trace amounts of plastic fiber were seen in all species except shiner perch. All exposure to sediment appeared to have occurred in the top 2 cm of the sediment column, or as contact with flocculent material on plants or hard substrates, or even in the water column, as some fine sand grains were seen in all fish, even anchovy. There was no conclusive evidence of site-specific foraging (site fidelity). The best spatial coverage was for topsmelt, and these fish appear to have fed opportunistically, with some evidence for having fed outside San Leandro Bay.

Habitat Restoration in the Sacramento-San Joaquin Delta and Suisun Marsh: A Review of Science Programs

Delta Stewardship Council (Delta Council) | April 25th, 2013

Current plans call for the restoration of tens of thousands of acres of mainly intertidal habitat in the Sacramento-San Joaquin Delta and Suisun Marsh. Restoration on thi

Current plans call for the restoration of tens of thousands of acres of mainly intertidal habitat in the Sacramento-San Joaquin Delta and Suisun Marsh. Restoration on this scale presents both formidable challenges and tremendous opportunities. As part of its legislatively mandated oversight of Delta science programs, the Delta Independent Science Board reviewed these habitat restoration efforts. We held discussions with individuals from state and federal agencies, NGOs, consulting firms, and universities. We were impressed by their dedication, enthusiasm, and knowledge, as well as by the scientific and institutional challenges they face. Our findings and observations about the restoration efforts are grouped under a series of criteria for a successful restoration program. In such a program: the goals are clearly articulated; the design incorporates spatial and temporal context, adaptive management and flexibility, and monitoring; modeling is used in design and evaluation; planning and implementation are coordinated among projects; the necessary scientific expertise is available; and stakeholders are involved early and often. Our findings and recommendations agree with those reached independently by National Research Council (NRC) panels. For convenience, as in the Delta Plan, we use "the Delta" to encompass both the statutory Delta and Suisun Marsh.

Habitat-Specific Foraging by Striped Bass (Morone saxatilis) in the San Francisco Estuary, California: Implications for Tidal Restoration

University of California, Davis (UC Davis) | December 1st, 2022

Non-native predatory fish strongly affect aquatic communities, and anthropogenic habitat alterations can exacerbate their effects. Loss of natural habitat, and restorati

Non-native predatory fish strongly affect aquatic communities, and anthropogenic habitat alterations can exacerbate their effects. Loss of natural habitat, and restoration actions that reverse habitat loss, can modify relationships between non-native predators and prey. Predicting how these relationships will change is often difficult because insufficient information exists on the habitat-specific feeding ecology of non-native predators. To address this information gap, we examined diets of non-native Striped Bass (Morone saxatilis; 63 to 671 mm standard length; estimated age 1 to 5 yrs) in the San Francisco Estuary during spring and summer in three habitat types—marsh, shoal, and channel—with the marsh habitat type serving as a model for ongoing and future restoration. Based on a preyspecific index of relative importance, Striped Bass diets were dominated by macroinvertebrates in spring and summer (amphipods in spring, decapods and isopods in summer). In spring, diets were relatively consistent across habitats. In summer, marsh diets were dominated by sphaeromatid isopods and shoal/channel diets by idoteid amphipods and decapods. Striped Bass consumed a variety of native and non-native fishes, primarily Prickly Sculpin (Cottus asper) and Gobiidae. The highest importance of fish prey was in the marsh in spring (~ 40% prey weight), and fish prey comprised less than 25% prey weight in all other season/habitat combinations. Linear discriminant analyses suggested that marsh foraging was prevalent in Striped Bass collected in other habitats, mostly because of the predominance of marsh-associated invertebrates found in the stomachs of individual Striped Bass collected outside the marsh. Striped Bass diets differ across habitats, with marsh foraging important to Striped Bass regardless of collection location. This information can be used to forecast the potential utilization of restored habitats by this non-native piscivore.

Haven or Hazard: The Ecology and Future of the Salton Sea

Pacific Institute | February 1st, 1999

California’s Salton Sea is a fertile oasis in the hostile desert of south-eastern California. It has been adopted by millions of birds migrating along the Pacific Flywa

California’s Salton Sea is a fertile oasis in the hostile desert of south-eastern California. It has been adopted by millions of birds migrating along the Pacific Flyway and also attracts human anglers and boaters. Rehabilitating the Salton Sea presents a huge challenge to the local, state, and federal officials that share responsibility for its health, as well as the health of those in surrounding communities. Originally published in February 1999,  Haven or Hazard: The Ecology and Future of the Salton Sea looks in detail at the condition of the Sea, the threats to the area, and possible solutions to protect its value for animals and people.

Hazard’s Toll: The Costs of Inaction at the Salton Sea

Pacific Institute | September 3rd, 2014

The declining Salton Sea will impose massive public health and environmental costs on local residents and Californians generally, as described in the Pacific Institute re

The declining Salton Sea will impose massive public health and environmental costs on local residents and Californians generally, as described in the Pacific Institute report Hazard’s Toll. The continued failure to protect and preserve the Salton Sea, worsening air quality and the loss of valuable ecological habitat – combined with diminished recreational revenue and property devaluation – could cost as much as $70 billion over the next 30 years. The high costs of California’s 2007 plan for the Salton Sea have inhibited deliberation and deterred any meaningful investment in revitalizing the Salton Sea. Many decision-makers assume that delaying action at the Salton Sea will result in business as usual, with no additional costs. Hazard’s Toll makes clear that this is not the case. Because the Salton Sea has changed over the past decade and will soon enter a period of very rapid decline, the costs of inaction are escalating rapidly. Even at the low end of the costs estimated in Hazard’s Toll, the long-term social and economic costs of a deteriorating Salton Sea could approach $29 billion, well in excess of the project cost of the state’s plan. The consequences of continued inaction at the Salton Sea will be felt most directly by the 650,000 people who live in harm’s way of the Salton Sea’s dust, as well as by the birds and other life that depend on the lake. Hazard’s Toll estimates the costs of these consequences, for the first time. These considerable costs demonstrate the urgent need for action at the Salton Sea. The report also highlights a large number of important data gaps that should be addressed in the near future. Despite many decades of study and the impending decline of the Salton Sea, we still lack information on many factors affecting life and the economy in the region. These factors, combined with general uncertainty about population growth rates, climate change, and changing hydrologic conditions, suggest that the above estimates indicate a general magnitude of potential future costs, rather than precise projections.

Health of Native Riparian Vegetation and its Relation to Hydrologic Conditions along the Mojave River, Southern California

U.S. Geological Survey (USGS) | July 15th, 1999