Simulated Limnological Effects of the Shasta Lake Temperature Control Device

Abstract

We estimated the effects of a temperature control device (TCD) on a suite of thermodynamic and limnological attributes for a large storage reservoir, Shasta Lake, in northern California. Shasta Dam was constructed in 1945 with a fixed-elevation penstock. The TCD was installed in 1997 to improve downstream temperatures for endangered salmonids by releasing epilimnetic waters in the winter/spring and hypolimnetic waters in the summer/fall. We calibrated a two-dimensional hydrodynamic reservoir water quality model, CE-QUAL-W2, and applied a structured design-of-experiment simulation procedure to predict the principal limnological effects of the TCD under a variety of environmental scenarios. Calibration goodness-of-fit ranged from good to poor depending on the constituent simulated, with an R2 of 0.9 for water temperature but 0.3 for phytoplankton. Although the chemical and thermal characteristics of the discharge changed markedly, the reservoir's characteristics remained relatively unchanged. Simulations showed the TCD causing an earlier onset and shorter duration of summer stratification, but no dramatic affect on Shasta's nutrient composition. Peak inreservoir phytoplankton production may begin earlier and be stronger in the fall with the TCD, while outfall phytoplankton concentrations may be much greater in the spring. Many model predictions differed from our a priori expectations that had been shaped by an intensive, but limited-duration, data collection effort. Hydrologic and meteorological variables, most notably reservoir carryover storage at the beginning of the calendar year, influenced model predictions much more strongly than the TCD. Model results indicate that greater control over reservoir limnology and release quality may be gained by carefully managing reservoir volume through the year than with the TCD alone.

Land use and land cover tools for climate adaptation

“…The depth and volume of a storage reservoir may influence its ability to buffer climate-driven changes in stream water temperature, but the strength and direction of such interactions varies. Rapid heating of shallow reservoirs can exacerbate down-stream temperature extremes (Gooseff et al 2005), while releases from deep, cold reservoirs can lower temperature and avoid ecological impacts of temperature-sensitive species like salmon (Bartholow et al 2001). Urban land uses can also contribute to aquatic temperature regimes.…”

Modeling hydrothermal, suspended solids transport and residence time in a deep reservoir

“…The W2 model uses a numerical scheme for a direct coupling between hydrodynamic and water quality simulations. The W2 model has been widely employed in many stratified lakes and reservoirs (Bartholow et al 2001;Kuo et al 2003;Sullivan et al 2003;Kim and Kim 2006;Gelda and Effler 2007;Zhang et al 2008;Afshar and Saadatpour 2009;Chung and Gu 2009;Etemad-Shahidi et al 2009). …”

Reservoir Operation Rules for Controlling Algal Blooms in a Tributary to the Impoundment of Three Gorges Dam

“…In Section 2, the study area is introduced in detail. From consideration of remarkable vertical flow structure of TGR as a river-type reservoir, a hydrodynamic and water quality model for the mainstream of TGR and tributary XXR (TGR-XXR model) is developed and calibrated based on the CE-QUAL-W2 model that has been applied successfully to many lakes, estuaries and reservoirs [29][30][31][32][33][34]. In Section 3, water movement and algal bloom process in XXR are simulated and analyzed under 11 different scenarios of short-term daily water discharge fluctuations or medium-term water level variations using chlorophyll a as the indicator for algal blooms.…”