Fort Hood Data Summary

(Storm Water Data)

 

Fort Hood streams are monitored using ISCO 4230 Bubble Flow Meters and ISCO 3700 Automatic Water Samplers. A typical BREC monitoring station is shown in this photo:  

 

 

 

 

 

 

 

The equipment includes: shelter, rain gauge (top of shelter on left) the 3700 water sampler, 4230 Flow Meter, and power system (battery - located in blue tray-  and solar panel - located on top center of shelter). The 4230 Bubble Flow Meters have programmed to initiate storm water sampling when streams rise above a determined depth (the programmed depth is site specific for each of the 13 locations). 

Three water samples are used to estimate loading for each storm event using the following protocol:

  •  First sample bottle taken for laboratory analysis is selected from the sample that is collected closest to one-foot above base flow (the 4230 hydrograph records depth, and time when each sample is collected)

  • Second water sample selected for laboratory analysis is collected nearest peak of hydrograph 

  • Third sample is selected at the mid-point between initiation and max on the descending arm of hydrograph  

  •  Samples and data are retrieved from the field and delivered to the laboratory after storm events.

 Record keeping, Field Data protocol:

  • Retrieved weekly or following storm water runoff event from ISCO 4230/6712 Bubble Flow Meter 

  • Stored and managed in ISCO FlowLink database software Parameters stored in FlowLink database include: Time, Level, Flow, and Precipitation. FlowLink allows the manipulation and exportation of data and summarizes it over any selected time interval

Data is stored and managed in a BREC Water Science Laboratory Database.  

  •  Lab ID number (sequential)

  • Sample collection date 

  • Location

  • Sample type (grab, storm)

  • Field comments

  • Bottle number (from ISCO 3700 Automated Sampler) 

  • Lab processing date 

  • Data - (NO3, PO4, TSS, etc.) 

  • Lab comments

Data Evaluation

  • Flow is determined from measured level or stage and slope/area method.. 

  • Open channel estimated of flow based on level using the Manning formula. 

  • Channel shape, slope and roughness is determined for each gauging location; stage/discharge curve developed with FlowMaster (Haestad Methods).

  • Loading Calculation; ISCO FlowLink data (stream flow and sampler events) exported to Excel for merging with laboratory data from BREC Water Quality Database 

  • Field data associated with laboratory data to estimate loading

    • Determine time intervals between samples are determined 

    • Determine sample concentrations that are associated with time intervals

    • Determine flow volume for a time interval.  The flow volume is multiplied by concentration to give load estimates for each time interval 

    • Determine loads for each time interval, which are summed for individual storm loads

    • Maintain final loading estimates in an MS Access database for analysis and storage.

 

Data Summary

The following charts were prepared using  Storm Water Samples collected during 1996-2001. Storm water samples are collected during storm events using ISCO 3700 auto samplers.  Samples were analyzed in our laboratory using QAQP procedures and SOP's developed specifically for the Fort Hood Water Quality Project using the same protocol used for grab samples.  The primary focus for storm samples  is sediment determination, however our evaluation of storm samples includes:  Nitrates, Ortho Phosphates, TSS (sediment) rainfall, and flow. These four charts represent only nitrate concentrations during the dates storm events were recorded, it is necessary to integrate this data with flow data to calculate stream loading during these events.

  • House Creek at FM 116 is located just down stream from a waste water treatment area and is upstream from Fort Hood. Runoff during periods of storm events is from range lands and the waste treatment plant.

 

 

 

  • House Creek at West Range Road is in mid-Fort Hood and located just above the confluence with Cowhouse Creek. 

 

 

 

  • The Cowhouse Creek at FM 116 sampling site is located at the point where the Cowhouse enters Fort Hood. Cowhouse Creek is a major Leon River sub-watershed which flows through Fort Hood and directly into Lake Belton. Upstream from Fort Hood Cowhouse Creek drainage area is predominantly rangeland.

 

  • Cowhouse at West Range Road, nitrate concentrations are usually similar to those from the FM116 site. Flow during the summer months and periods of drought are often negligible..  

 

 

The final figure in this two part series is a comparison of loading determined by integrating grab sample data (Base Load) and storm water data (Storm Load)  during the year 2000. To evaluate “background” stream conditions, monthly grab samples are collected during periods of “normal flow” to evaluate overall stream health. To determine water quality conditions during storm water events when both stream flow (quantity) and velocity (movement down stream) is dramatically increased, ISCO Storm Water monitors and samplers are used. 

Problems arise when monthly grab sampling data is used to predict water quality conditions and determine total loading during storm events. The pollution load dramatically increases during a storm, which is rarely accounted for by the usual monthly sampling data.  Using monthly sample data in this manner assumes that the sample concentration represents the concentration in the stream between samples.  This leads to errors when concentrations are not steady, which is the case during storms. 

 Most of the total yearly stream loading is transported during storm periods. Therefore, to determine accurate stream loading, storms events need to be intensively sampled.  To demonstrate these differences, BREC scientists have used data collected from one site on Cowhouse Creek during 2000 to express the loading differences. 

 

 

 

BREC Grab Sample Data Summary

Fort Hood Main Page


March 5, 2002
Dennis Hoffman, Project Leader;