HIC MEETING July 12, 2005

Streamflow Regulation Accounting

by

Tom Gurss

Missouri Basin River Forecast Center

National Weather Service

Pleasant Hill, MO

Tom.gurss@noaa.gov

REGULATION ISSUES

How do we provide long term probabilistic forecasts for locations heavily regulated for flood control, navigation, instream flows, irrigation, municipal water supply, power generation, etc.?

SRA GOALS

Evaluate existing data sources and modeling approaches and develop a generalized strategy to account for regulation in long-range forecasts.

Evaluate need for new tools, cost of development, and accuracy.

SRA TASKS

Phase 1--2004. Gather input and ideas from RFCs Develop strategies to better apply

current NWSRFS procedures Develop National Strategy Plan Develop South Platte

Implementation Plan as prototype model

Collect regulation data for South Platte River

SRA TASKS

Phase 2—2004-2005. Implementation of South Platte Plan on

Cache La Poudre River Basin Evaluate the strategies and identify

limitations in data, procedures and technologies

Test 3 different modeling approaches Evaluate effectiveness by generating

forecast verification statistics using hindcasting with ESPVS and ProbVS

Recommend Enhancements Update Strategy Plans as needed

SRA TASKS

Phase 2—2004-2005 (cont) Poudre River chosen because of

extensive available historical data Trans-basin imports Multiple upper elevation reservoirs Dozens of lower elevation off channel

storage areas Multiple re-use of irrigation water Base flows depend on return flows Water Rights huge factor as water is

traded between entities and storage facilities

SRA TASKS

Phase 2—2004-2005 Verification.

Evaluated 90-day probabilistic forecasts for April 1 and July 1 for volume, maximum, and minimum

Looked at RPS, RPSS, reliability, and discrimination

SRA TASKS

Phase 2—2004-2005 Results. Complex operations required to describe

psuedo reservoirs with very little data to adjust model to.

Verification showed some skill for maximum flows and volume, but little or no skill for minimum flows. Climatology better at some locations for low flows.

Verification statistics highly dependent on bin selection with limited sample size.

SRA TASKS Phase 3—2005-6.

Expand implementation plan into other sub-basins with less data, but similar regulation—Big Thompson and St. Vrain Rivers

Simplify strategy based on results of Phase 2

Generate verification statistics using hindcasting

Revise list of enhancements and strategy plans

SRA TASKS Phase 3—2005-6 Results.

Simplified operations provided similar verification statistics as the more complex operations for maximum flows, but little or no skill for minimum flows.

SRA TASKS

Phase 4—2006-8 (Proposed). Expand implementation into other

sub-basins with different types of regulation activities

Revise list of enhancements and strategy plans

Lessons Learned Poor verification statistics in low-flow

forecasts because of inability to adequately simulate human behavior’s effects

Data to support complex operations lackingOperational concerns using complex RES-J

operationsLimitations due to changing demands, uses,

and variance from rules.Tools Enhancements would simplify

operations

Future Concerns Need to decide whether low-flow forecasting of

streams with heavy regulation is adding value to historical distributions

Regulation in conjunction with Groundwater Pumping of Alluvial Aquifer

Power Generation

Large Multiple Reservoir System Simulation

Additional Tools Enhancements