Snowmelt Runoff and Water Yield Along Elevation and Temperature Gradients in California’s Southern Sierra Nevada1

Hunsaker, Carolyn T., Thomas W. Whitaker, and Roger C. Bales, 2012. Snowmelt Runoff and Water Yield Along Elevation and Temperature Gradients in California’s Southern Sierra Nevada. Journal of the American Water Resources Association (JAWRA) 48(4): 667‐678. DOI: 10.1111/j.1752‐1688.2012.00641.x Abstract: Differences in hydrologic response across the rain‐snow transition in the southern Sierra Nevada were studied in eight headwater catchments – the Kings River Experimental Watersheds – using continuous precipitation, snowpack, and streamflow measurements. The annual runoff ratio (discharge divided by precipitation) increased about 0.1 per 300 m of mean catchment elevation over the range 1,800‐2,400 m. Higher‐elevation catchments have lower vegetation density, shallow soils with rapid permeability, and a shorter growing season when compared with those at lower elevations. Average annual temperatures ranged from 6.8°C at 2,400 m to 8.6 at 1,950 m elevation, with annual precipitation being 75‐95% snow at the highest elevations vs. 20‐50% at the lowest. Peak discharge lagged peak snow accumulation on the order of 60 days at the higher elevations and 20 to 30 days at the lower elevations. Snowmelt dominated the daily streamflow cycle over a period of about 30 days in higher elevation catchments, followed by a 15‐day transition to evapotranspiration dominating the daily streamflow cycle. Discharge from lower elevation catchments was rainfall dominated in spring, with the transition to evapotranspiration dominance being less distinct. Climate warming that results in a longer growing season and a shift from snow to rain would result in earlier runoff and a lower runoff ratio.     

Organic matter source discrimination by humic acid characterization: Synchronous scan fluorescence spectroscopy and Ferrate(VI)

In this study, seven soil and sedimentary humic acid samples were analyzed by synchronous scan fluorescence (SSF) spectroscopy. The spectra of these humic acids were compared to each other and characterized, based on three major SSF peaks centered at approximately 281, 367 and 470 nm. Intensity ratios were calculated based on these peaks that were used to numerically assist in source discrimination. All humic acid samples were then reacted with Ferrate(VI) and were again analyzed with SSF. Upon the addition of Ferrate(VI) SSF spectra were obtained which more readily differentiated humic acid source. This method will assist geochemists and water management districts in tracing sources of organic matter to receiving water bodies and may aid in the elucidation of the chemical nature of humic acids.     

Product Guide/1988

Investigation, mitigation, and clean-up of hazardous materials at Superfund sites normally requires on-site workers to perform hazardous and sometimes potentially dangerous functions. Such functions include site surveys and the reconnaissance for airborne and buried toxic environmental contaminants. Airborne contaminants of concern usually emanate from spilled materials and require monitoring the air at the perimeter and throughout the clean-up site to ascertain the extent of contamination. Buried contaminants of major concern are often the result of leaking underground drums containing toxic wastes and require "reconnaissance excavations" to determine their location. Workers conducting on-site air monitoring risk dermal, ocular and inhalation exposure to hazardous chemicals, while those performing excavations also risk the potential exposure to fire, explosion, and other physical injury. EPA's current efforts to protect its workers and mitigate these risks include the use of robotic devices. Using robots offers the ultimate in personnel protection by removing the worker from the site of potential exposure, especially during site investigations, when there is almost always a certain encounter with unknown chemical wastes having unknown toxicity.

This paper describes the demonstration of a commercially-available robotic plat form modified and equipped for air monitoring and the ongoing research for the development of a ground penetrating radar (GPR) system to detect buried chemical waste drums. These robotic devices can ultimately be routinely deployed in the field for the purpose of conducting inherently safe reconnaissance activities during Superfund / SARA remedial operations.     

Dry Wetlands: Nutrient Dynamics in Ephemeral Constructed Stormwater Wetlands

Environmental Management - Constructed stormwater wetlands (CSWs) are used to address contaminants in urban stormwater such as nitrogen (N) and phosphorus (P), but their performance is variable....     

Elevated pCO2 causes developmental delay in early larval Pacific oysters, Crassostrea gigas

Increasing atmospheric CO₂ equilibrates with surface seawater, elevating the concentration of aqueous hydrogen ions. This process, ocean acidification, is a future and contemporary concern for aquatic organisms, causing failures in Pacific oyster (Crassostrea gigas) aquaculture. This experiment determines the effect of elevated pCO₂ on the early development of C. gigas larvae from a wild Pacific Northwest population. Adults were collected from Friday Harbor, Washington, USA (48°31.7′N, 12°1.1′W) and spawned in July 2011. Larvae were exposed to Ambient (400 μatm CO₂), MidCO₂ (700 μatm), or HighCO₂ (1,000 μatm). After 24 h, a greater proportion of larvae in the HighCO₂ treatment were calcified as compared to Ambient. This unexpected observation is attributed to increased metabolic rate coupled with sufficient energy resources. Oyster larvae raised at HighCO₂ showed evidence of a developmental delay by 3 days post-fertilization, which resulted in smaller larvae that were less calcified.     

Groundwater protection in mixed land-use aquifers

Compared with groundwater pollution episodes of a point-source nature, nonpoint-source contamination makes for particularly difficult policy design. This is especially true in the context of a mixed land-use aquifer, where the same pollutant may derive from various human land-use activities and in different concentrations. To data, the emprirical literature attempting to estimate the relative loadings of pollutants from alternative land uses is rather sparse. Yet this information is vital to a variety of numerical computer models used to predict likelihood of groundwater contamination, and the statistical results are useful in their own right for regional policy formation. Regression analysis is applied to estimate loadings of nitrate and sodium from various land uses. The model is then used to illustrate how well-intended local groundwater protection policies that fail to recognize land-use substitution and cross-pollutant effects may be misdirected.