Comparing Futures for the Sacramento-San Joaquin Delta

Analyzes expected changes to the hub of California's water system and presents a comparative assessment of four water management strategies for environmental sustainability and water supply reliability. Discusses policy and regulatory implications

Redshifts and Velocity Dispersions of Galaxy Clusters in the Horologium-Reticulum Supercluster

We present 118 new optical redshifts for galaxies in 12 clusters in the Horologium-Reticulum supercluster (HRS) of galaxies. For 76 galaxies, the data were obtained with the Dual Beam Spectrograph on the 2.3m telescope of the Australian National University at Siding Spring Observatory. After combining 42 previously unpublished redshifts with our new sample, we determine mean redshifts and velocity dispersions for 13 clusters, in which previous observational data were sparse. In six of the 13 clusters, the newly determined mean redshifts differ by more than 750 km/s from the published values. In the case of three clusters, A3047, A3109, and A3120, the redshift data indicate the presence of multiple components along the line of sight. The new cluster redshifts, when combined with other reliable mean redshifts for clusters in the HRS, are found to be distinctly bi-modal. Furthermore, the two redshift components are consistent with the bi-modal redshift distribution found for the inter-cluster galaxies in the HRS by Fleenor et al. (2005).Comment: 13 pages, 3 figures, Accepted to A

Inland Pacific Northwest pasture calendar

The Inland Pacific Northwest (PNW) region, historically referred to as the 'Inland Empire', extends from the Cascade Mountains in the west to former Glacial Lake Missoula in the Rockies in the east and from the Canadian border in the north past the Snake River Canyon in the south. The greatest agricultural enterprises are hay (from various forage species), irrigated and non-irrigated grassland pastures, rangelands, and livestock production. It is also home to numerous wildlife species and flyways for migrating birds. The Inland PNW Pasture Calendar is designed to be a comprehensive guide for improved grassland management in support of forage-livestock systems. Applying the principles described will lead to improved regional economic, ecological, and social sustainability. This publication describes the opportunities and challenges of sustainably raising harvested and grazed forages and developing forage-livestock systems in this incredibly diverse environment. Appendix Chapters provide key information on grass / legume / forb species, how pasture species grow and regrow, soil nutrient management and organic matter, grazing philosophies and systems, matching grazing needs for pasture production, and forage-related animal health issues. Learning these key principles and following best management practices described will lead to improved sustainability of forage-livestock systems

Large-Scale Velocity Structures in the Horologium-Reticulum Supercluster

We present 547 optical redshifts obtained for galaxies in the region of the Horologium-Reticulum Supercluster (HRS) using the 6dF multi-fiber spectrograph on the UK Schmidt Telescope at the Anglo Australian Observatory. The HRS covers an area of more than 12deg x 12deg on the sky centered at approximately RA = 03h19m, DEC = -50deg 02amin. Our 6dF observations concentrate upon the inter-cluster regions of the HRS, from which we describe four primary results. First, the HRS spans at least the redshift range from 17,000 to 22,500 km s^-1. Second, the overdensity of galaxies in the inter-cluster regions of the HRS in this redshift range is estimated to be 2.4, or del rho/ rho ~ 1.4. Third, we find a systematic trend of increasing redshift along a Southeast-Northwest (SE-NW) spatial axis in the HRS, in that the mean redshift of HRS members increases by more than 1500 km s^-1 from SE to NW over a 12 deg region. Fourth, the HRS is bi-modal in redshift with a separation of ~ 2500 km s^-1 (35 Mpc) between the higher and lower redshift peaks. This fact is particularly evident if the above spatial-redshift trend is fitted and removed. In short, the HRS appears to consist of two components in redshift space, each one exhibiting a similar systematic spatial-redshift trend along a SE-NW axis. Lastly, we compare these results from the HRS with the Shapley supercluster and find similar properties and large-scale features.Comment: 20 pages, 9 figures, accepted to A

Physical Controls on the Distribution of the Submersed Aquatic Weed Egeria densa in the Sacramento–San Joaquin Delta and Implications for Habitat Restoration

The invasive aquatic plant Egeria densa (Brazilian waterweed) is a submersed aquatic plant that has expanded its distribution in both its native and introduced range. Because the plant grows so densely, it can become a problem for management of waterways and habitat restoration projects. It is difficult to remove once established and mechanical and chemical controls have shown limited effectiveness. Here we analyze the distribution of E. densa in the Sacramento–San Joaquin Delta (the Delta) of California, USA, using environmental variables that include mean water velocity, mean water turbidity, and water column depth. We found that increasing water column depth strongly limited E. densa occurrence, especially when depth at mean lower low water (MLLW) exceeds 2 m. The highest probability of occurrence occurred at locations with a water column depth of −1 to 2 m at MLLW. Turbidity had a reliably negative effect on E. densa occurrence; as water clarity has increased in the Delta, it has likely favored the spread of the plant. Neither mean water velocity nor maximum water velocity had a reliable effect on E. densa probability, in spite of scientific and observational evidence that it is sensitive to flows. These results suggest potentially serious problems with restoration projects that emphasize shallow water habitat in the range favored by E. densa. Without some way to manage spread of the plant—through spraying, sediment loading, or gating—channels in such projects are at risk of being taken over by E. densa. However, these results should be interpreted in light of the fact that water outflow in water year 2008 was very low, and that E. densa abundance may be partially controlled by higher water flows than those considered here

Physical Controls on the Distribution of the Submersed Aquatic Weed Egeria densa in the Sacramento–San Joaquin Delta and Implications for Habitat Restoration

The invasive aquatic plant Egeria densa (Brazilian waterweed) is a submersed aquatic plant that has expanded its distribution in both its native and introduced range. Because the plant grows so densely, it can become a problem for management of waterways and habitat restoration projects. It is difficult to remove once established and mechanical and chemical controls have shown limited effectiveness. Here we analyze the distribution of E. densa in the Sacramento–San Joaquin Delta (the Delta) of California, USA, using environmental variables that include mean water velocity, mean water turbidity, and water column depth. We found that increasing water column depth strongly limited E. densa occurrence, especially when depth at mean lower low water (MLLW) exceeds 2 m. The highest probability of occurrence occurred at locations with a water column depth of −1 to 2 m at MLLW. Turbidity had a reliably negative effect on E. densa occurrence; as water clarity has increased in the Delta, it has likely favored the spread of the plant. Neither mean water velocity nor maximum water velocity had a reliable effect on E. densa probability, in spite of scientific and observational evidence that it is sensitive to flows. These results suggest potentially serious problems with restoration projects that emphasize shallow water habitat in the range favored by E. densa. Without some way to manage spread of the plant—through spraying, sediment loading, or gating—channels in such projects are at risk of being taken over by E. densa. However, these results should be interpreted in light of the fact that water outflow in water year 2008 was very low, and that E. densa abundance may be partially controlled by higher water flows than those considered here

Physical Controls on the Distribution of the Submersed Aquatic Weed <i>Egeria densa</i> in the Sacramento–San Joaquin Delta and Implications for Habitat Restoration

doi: http://dx.doi.org/10.15447/sfews.2016v14iss1art4The invasive aquatic plant Egeria densa (Brazilian waterweed) is a submersed aquatic plant that has expanded its distribution in both its native and introduced range. Because the plant grows so densely, it can become a problem for management of waterways and habitat restoration projects. It is difficult to remove once established and mechanical and chemical controls have shown limited effectiveness. Here we analyze the distribution of E. densa in the Sacramento–San Joaquin Delta (the Delta) of California, USA, using environmental variables that include mean water velocity, mean water turbidity, and water column depth. We found that increasing water column depth strongly limited E. densa occurrence, especially when depth at mean lower low water (MLLW) exceeds 2 m. The highest probability of occurrence occurred at locations with a water column depth of −1 to 2 m at MLLW. Turbidity had a reliably negative effect on E. densa occurrence; as water clarity has increased in the Delta, it has likely favored the spread of the plant. Neither mean water velocity nor maximum water velocity had a reliable effect on E. densa probability, in spite of scientific and observational evidence that it is sensitive to flows. These results suggest potentially serious problems with restoration projects that emphasize shallow water habitat in the range favored by E. densa. Without some way to manage spread of the plant—through spraying, sediment loading, or gating—channels in such projects are at risk of being taken over by E. densa. However, these results should be interpreted in light of the fact that water outflow in water year 2008 was very low, and that E. densa abundance may be partially controlled by higher water flows than those considered here.</p

Agricultural Losses from Salinity in California’s Sacramento-San Joaquin Delta

Sea level rise, large-scale flooding, and new conveyance arrangements for water exports may increase future water salinity for local agricultural production in California’s Sacramento–San Joaquin Delta. Increasing salinity in crop root zones often decreases crop yields and crop revenues. Salinity effects are nonlinear, and vary with crop choice and other factors including drainage and residence time of irrigation water. Here, we explore changes in agricultural production in the Delta under various combinations of water management, large-scale flooding, and future sea level rise. Water management alternatives include through-Delta water exports (current conditions), dual conveyance (through-Delta and a 6,700 Mm3 yr‑1 [or 7500 cfs] capacity peripheral canal or tunnel) and the flooding of five western islands with and without peripheral exports. We employ results from previous hydrodynamic simulations of likely changes in salinity for irrigation water at points in the Delta. We connect these irrigation water salinity values into a detailed agro-economic model of Delta agriculture to estimate local crop yield and farm revenue losses. Previous hydrodynamic modeling work shows that sea level rise is likely to increase salinity from 4% to 130% in this century, depending on the increase in sea level and location. Changes in water management under dual conveyance increase salinity mostly in the western Delta, and to a lesser extent in the north, where current salinity levels are now quite low. Because locations likely to experience the largest salinity increases already have a lower-value crop mix, the worst-case losses are less than 1% of total Delta crop revenues. This result also holds for salinity increases from permanent flooding of western islands that serve as a salinity barrier. Our results suggest that salinity increases could have much smaller economic effects on Delta farming than other likely changes in the Delta such as retirement of agricultural lands after large-scale flooding and habitat development. Integrating hydrodynamic, water salinity, and economic models can provide insights into controversial management issues. </p

Agricultural Losses from Salinity in California’s Sacramento-San Joaquin Delta

Sea level rise, large-scale flooding, and new conveyance arrangements for water exports may increase future water salinity for local agricultural production in California’s Sacramento–San Joaquin Delta. Increasing salinity in crop root zones often decreases crop yields and crop revenues. Salinity effects are nonlinear, and vary with crop choice and other factors including drainage and residence time of irrigation water. Here, we explore changes in agricultural production in the Delta under various combinations of water management, large-scale flooding, and future sea level rise. Water management alternatives include through-Delta water exports (current conditions), dual conveyance (through-Delta and a 6,700&nbsp;Mm3 yr‑1 [or 7500 cfs] capacity peripheral canal or tunnel) and the flooding of five western islands with and without peripheral exports. We employ results from previous hydrodynamic simulations of likely changes in salinity for irrigation water at points in the Delta. We connect these irrigation water salinity values into a detailed agro-economic model of Delta agriculture to estimate local crop yield and farm revenue losses. Previous hydrodynamic modeling work shows that sea level rise is likely to increase salinity from 4% to 130% in this century, depending on the increase in sea level and location. Changes in water management under dual conveyance increase salinity mostly in the western Delta, and to a lesser extent in the north, where current salinity levels are now quite low. Because locations likely to experience the largest salinity increases already have a lower-value crop mix, the worst-case losses are less than 1% of total Delta crop revenues. This result also holds for salinity increases from permanent flooding of western islands that serve as a salinity barrier. Our results suggest that salinity increases could have much smaller economic effects on Delta farming than other likely changes in the Delta such as retirement of agricultural lands after large-scale flooding and habitat development. Integrating hydrodynamic, water salinity, and economic models can provide insights into controversial management issues.&nbsp