CBWMPhase 5 Status Report

Modeling Subcommittee MeetingModeling Subcommittee Meeting

October 2, 2002October 2, 2002

Overview

• Model structure and Model structure and responsibilitiesresponsibilities

• Model segmentationModel segmentation

• Precipitation modelingPrecipitation modeling

Model Responsibilities

• Source dataSource data

/p50X/pp/data//p50X/pp/data/ CBPCBP• External transfer module (scripts)External transfer module (scripts)

/p50X/pp/etm//p50X/pp/etm/ CBPCBP• Model parametersModel parameters

/p50X/pp/lib/catalogs/modules//p50X/pp/lib/catalogs/modules/ USGSUSGS• Watershed-reach connection filesWatershed-reach connection files

/p50X/pp/lib/connect//p50X/pp/lib/connect/ USGSUSGS

Segmentation

• Downstream ID has been Downstream ID has been added to all reaches in the added to all reaches in the Chesapeake Bay Watershed Chesapeake Bay Watershed except for those draining except for those draining directly to the estuary. (Their ID directly to the estuary. (Their ID is zero.)is zero.)

• Working on attributing the Working on attributing the southern Virginia watersheds southern Virginia watersheds with DSID.with DSID.

Segmentation

• Reaches and watersheds have Reaches and watersheds have been reconnected so that we been reconnected so that we know what streams are in what know what streams are in what watersheds.watersheds.

• Working on transferring the Working on transferring the mean annual discharge mean annual discharge attributes to the watersheds so attributes to the watersheds so we have the flow attribute in the we have the flow attribute in the names. names.

Precipitation Modeling

• Objectives:Objectives:• Spatially distribute recorded point-Spatially distribute recorded point-

precipitation data to provide high-precipitation data to provide high-resolution, low-bias areal precipitation resolution, low-bias areal precipitation time-series data at an hourly time time-series data at an hourly time step for use as input to hydrologic step for use as input to hydrologic models.models.

• Provide areal precipitation time-series Provide areal precipitation time-series data that can be used in a consistent data that can be used in a consistent manner over a range of spatial manner over a range of spatial scales.scales.

Precipitation Modeling: Scope

• Data used to achieve these Data used to achieve these objectives are daily and hourly objectives are daily and hourly recorded precipitation totals recorded precipitation totals from climate stations within the from climate stations within the study area, including a 25-km study area, including a 25-km buffer around the area buffer around the area boundary.boundary.

• Precipitation data are from the Precipitation data are from the period 1985 through 2000.period 1985 through 2000.

Precipitation Modeling: Scope

• 487 daily-data 487 daily-data stationsstations

• 192 hourly-192 hourly-data stationsdata stations

Precipitation Modeling: Scope

• Daily precipitation data are Daily precipitation data are simulated for 10-km square grid simulated for 10-km square grid cells throughout the study area.cells throughout the study area.

• Daily precipitation for each FIPS2 Daily precipitation for each FIPS2 area within the study area is area within the study area is computed based on time-series computed based on time-series data from grid cells within each data from grid cells within each FIPS2 area.FIPS2 area.

xyz Methodology

• Multiple linear regression (MLR) Multiple linear regression (MLR) equations are developed for daily equations are developed for daily precipitation (precipitation (pp) in each of six sub-) in each of six sub-regions using independent regions using independent variables variables xx, , yy, and , and zz from climate from climate stations in each sub-region.stations in each sub-region.

• The general form of the MLR The general form of the MLR equation is:equation is:

0 1 2 3p b b x b y b z

Hourly Disaggregation

• Simulated daily precipitation data Simulated daily precipitation data are disaggregated into hourly data are disaggregated into hourly data using:using:• recorded hourly precipitation from the recorded hourly precipitation from the

nearest climate station, ornearest climate station, or

• Mean-hourly precipitation by month Mean-hourly precipitation by month and weather type.and weather type.

• Simulated daily Simulated daily pp totals are totals are preserved during disaggregation.preserved during disaggregation.

Mean-hourly rainfall (Feb)

Example Data

• 10x10km daily 10x10km daily datadata

• January, 1990January, 1990

• mm/daymm/day

Future Plans

• Complete trial Patuxent runComplete trial Patuxent run

• Complete F-tablesComplete F-tables

• Begin PEST implementationBegin PEST implementation

• Continue investigating inclusion Continue investigating inclusion of estimates of ground-water of estimates of ground-water residence timesresidence times

“on the graph paper”Phase 5 Patuxent Flow at Bowie

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