Cold Water Inflow into a Reservoir:A Field and Modeling Study

Rachel D. SimonsEast Bay Municipal Utility District

February 28, 2007

EBMUD Distribution System

San Francisco

Lower Mokelumne River

The Reservoir System

Camanche ReservoirPardee Reservoir

Upper Mokelumne River

Lower Mokelumne River

1 mile

Water not sent to EBMUD customers is released from Pardee to Camanche via the river

River

Pardee ReservoirMaximum Depth: 300 ftSurface Area: 2,400 acresStorage: 200 TAF

Camanche ReservoirMaximum Depth: 160 ft Surface Area: 8,300 acresStorage: 400 TAF

depth (ft)

Reservoir Background

Temperature Patterns

1 mile

Sample sites at deepest point near dam

Camanche Pardee

2006 Temperature (°C)

Minimum Reservoir Temperature

In general, Pardee stays colder than Camanche.

PardeeCamanche

2006

Questions ExploredWhat happens to the cold water released from Pardee before it reaches Camanche?

In particular, what is the influence of:• Warming in river• Stratification in Camanche• Unsteady flow (peaking for power generation)

To address these questions, we needed to:- Collect temperature field data (Part 1)- Develop a river model (Part 2)

Study Area1 - Water released from Pardee Dam2 - Water travels down river (~ 2 miles)3 - River plume plunges below surface of Camanche

Camanche Reservoir

Pardee Dam

River

Study Area

Part 1: Collect Field DataStation 1:Below Pardee Dam

Station 2:Camanche River Inflow

CamancheReservoir

Station 1: Below Pardee DamTemperatureProbe (4 in.)

Cable

Weight Stake

Station 2: Camanche River InflowPardee Dam Outflow

River Reservoir Surface

Station 2

Plunge Point

Camanche

* River length and plunge point location varies depending on the surface water elevation of Camanche

Station 2: Camanche River InflowMultiple probes needed to capture stratification

July 26, 2006

Station 2

Station 2: Temperature Probes

Weight

Changing Elevation

5 ft

Buoy on Line

7 Temperature Probes Probes attached to buoy

Part 2: Develop River ModelModel: River Modeling System (RMS4)Author: Tennessee Valley Authority

One-Dimensional Horizontal Model- ADYN: Hydrodynamics- RQUAL: Water Quality (Temperature)

Open Source Code

Main Advantages:• Incorporates river geometry with cross-sections• Can run at an hourly time step• Handles unsteady flow

River Geometry

Cross-Section Location

elevation (ft)

1

2

3

45

7

Pardee Dam

¼ mile

6

Digital Map from Aerial Topographic Survey

River Model Summary

Input: Pardee Dam Flow Rate & Temperature

Meteorological data:- Solar radiation- Cloud cover- Air temperature- Dew point- Wind speed

Output: River Temperature

River Geometry

Questions Explored

What happens to the cold water released from Pardee before it reaches Camanche?

In particular, what is the influence of:• Warming in river• Stratification in Camanche• Unsteady flow (peaking for power generation)

Pardee Dam Releases (River Flow)Temperature data collected: June 28 – December 13, 2006

Peaking for PowerGeneration

Temperature Below Pardee DamThe Coldest Water

River Warming: Model Results

Pardee ReleaseModel Output

Model Comparison to Field DataPardee Dam Outflow

River Reservoir Surface

Station 2

Plunge Point

1-D River Model Camanche

•Compare river model output to bottom probe at station 2•Theory: Cold water plume plunges below reservoir surfaceand runs along bottom

River WarmingPardee ReleaseModel OutputStation 2 bottom

River WarmingPardee ReleaseModel OutputStation 2 bottom

Temperature at Station 27 sensors

Stratification at Station 2SurfaceBottom

Stratification at Station 2SurfaceBottom

Plume Warming and Stratification

Pardee Dam Temperature

River Reservoir Surface

Station 2

Plunge Point

Camanche

Plume Warming: Temperature difference between Pardee Dam releaseand bottom of Station 2

Stratification: Temperature difference between surface and bottom of Station 2

Plume Warming and Stratification

StratificationWarming

Plume Warming and StratificationStratificationWarming

1,200 cfs Peaking 800 cfs Peaking

Talk SummaryWhat can we say about river warming, stratification in Camanche, and flow rate in relation to the Pardee cold water releases?

• Cold water released from Pardee Dam can be significantly warmed by both river travel and stratification in Camanche

• In some cases, higher flow rates reduce the amount of plume warming.

• Otherwise, a work in progress…