Central Indiana Water Resources Partnership

Watershed Contribution to Three Central Indiana Reservoirs: Characterization of Suspended Sediment and Dissolved Loads

• Introduction

• Study Site and Land Cover

• Methodology

• Common Land Use

• Watershed Sampling

• Watershed Contributions

• A Closer Look

• Conclusions

• Acknowledgements

Introduction

Water quality issues and nuisance causing taste and odor compounds have been among the most challenging problems facing the Indianapolis water supply. In order to resolve these issues, it is imperative to develop an understanding of drinking water quality as it relates to watershed dynamics. Therefore, a comprehensive watershed-scale research program was developed and implemented in the winter of 2003 on the three watersheds that most directly impact Indianapolis’ drinking water supply: Eagle Creek, Fall Creek, and Cicero Creek watersheds.

Study Site and Land Cover

Location

Each of the three watersheds is part of the Upper White River watershed. They lie north of the Indianapolis metropolitan area and drain into reservoirs that supply Indianapolis’ drinking water system. The watersheds are set within the Tipton Till Plain, a flat to gently rolling landscape formed from glacial deposits.

Watersheds and Their Associated Land Cover

Eagle Creek Watershed
Eagle Creek watershed has a watershed area of 162 mi2 above the dam.
In 1985, the Eagle Creek watershed was 2.2% urbanized (high and low density land cover), 12.4% forest, and 65.9% agriculture land cover.
By 2000, the Eagle Creek watershed was 4.3% urbanized, 9.3% forest, and 52% agriculture land cover.
Fall Creek Watershed
Fall Creek watershed has a watershed area of 215 mi2 above the dam.
In 1985, the Fall Creek watershed was 3.8% urbanized, 9.3% forest, and 68.8% agriculture.
By 2000, the Fall Creek watershed had reached 6.2% urbanized land cover and had fallen to 5.3% forest and 58.3% agriculture.
Cicero Creek Watershed
Cicero Creek watershed has a watershed area of 227 mi2 above the dam.
In 1985, the Cicero Creek watershed consisted of 1.5% urbanized, 3.3% forest, and 84.7% agriculture land cover.
By 2000, the Cicero Creek watershed was 2% urbanized, 2% forest, and 76.9% agriculture land cover.

Land cover patterns in Eagle Creek and Fall Creek watersheds were more dynamic than in Cicero Creek watershed. While the degree of change varied across the watersheds, the pattern of change by land cover type was consistent.
The largest increase for a particular land cover type occurred in the herbaceous (grassland) category, while the largest decrease occurred in the agriculture category for all three watersheds.

top of page

Methodology

In each of the three watersheds, water was sampled from select stream segments to document the contribution of suspended sediment, dissolved and sediment-associated components. Samples were [and continue to be] collected quarterly to characterize both base flow and storm flow (runoff) loadings from the watersheds.
Sampling for dissolved and suspended sediments was conducted during low flow when the estimated discharge was approximately equal to the mean monthly discharge for the season. Storm flow conditions were sampled when discharge exceeded a minimum of three times the mean flow for the season.
USGS stream gauges in Eagle Creek and Fall Creek watersheds are used to determine real-time streamflow. Because Cicero Creek has no active USGS stream gauge within its watershed above the reservoir, the nearest USGS gauge in Eagle Creek watershed is used as a proxy for Cicero Creek streamflow.

Common Land Use

Fields and mowed lawns are a common occurrence close to stream shorelines.

Corn fields are one of the most common crops found within each of the watersheds.

Soy bean is another common crop found within the central Indiana watersheds.

top of page

Watershed Sampling

Base flow sampling in Eagle Creek watershed during winter quarter 2003.

Fishback Creek subwatershed: 2/25/03

Base flow sampling in Eagle Creek watershed during spring quarter 2003.

Fishback Creek subwatershed: 5/21/03

Event flow sampling in Eagle Creek watershed during summer quarter 2003.

Fishback Creek subwatershed: 9/02/03

Watershed Contributions

Watershed contributions of both dissolved and suspended components vary significantly in magnitude and composition on a seasonal basis and with respect to land use in sub-watersheds.
Chloride concentrations in water samples are highest during base flow, especially in the winter quarter. Chloride is less concentrated during event flows, suggesting it is getting flushed with increased stream discharge. Chloride is a conservative tracer and should be diluted during events.

Suspended sediment concentrations are highest during event flows regardless of sampling season. Suspended sediment is highest during spring events for Eagle Creek and Cicero Creek watersheds. Fall Creek watershed, however, shows suspended sediment highest during winter event flows. Suspended sediment concentrations during the spring event in Fall Creek are nearly as high as those of winter.

Phosphorus concentrations of dissolved load are variable among the watersheds for each season sampled. Cicero Creek watershed shows highest P concentrations during winter base flow and spring event flow (no samples were collected for winter event flow). Eagle Creek and Fall Creek have highest P concentration during the spring event flow. Winter event flow samples also have high P concentrations.

Total Kjeldahl Nitrogen (TKN) has similar seasonal distribution in dissolved load as phosphorus. Concentrations are highest during event flows, particularly during the spring quarter. Winter nonevent concentrations in Cicero Creek watershed have surprisingly high concentrations as well.

Because of increased suspended sediment, higher phosphorus and TKN concentrations are observed during event flows for each watershed. Runoff from the watersheds is likely a major contributor to these parameters within each sub-watershed to streams.
 

top of page

Chloride

Suspended Sediments

top of page

Phosphorus

Total Kjeldahl Nitrogen

top of page

A Closer Look

Stream water discharge of contributing tributaries and sediment concentration suggest that some sub-watersheds contribute disproportionately higher sediment and chemical loads relative to their drainage area.

At low flow, as the area drained by Eagle Creek and its sub-watersheds increased, no significant increase in suspended sediment occurred. During an event flow, however, an increase in watershed area resulted in mostly a linear increase in suspended sediment load in the trunk streams of Eagle Creek watershed. Furthermore, the tributaries of Eagle Creek watershed illustrate disproportionate sediment contributions during event flows. Fishback Creek (Site 2) and School Branch (Site 1) show elevated suspended sediment concentrations during each seasonal sampling. Fishback Creek (Site 2) had the highest suspended sediment during spring quarter sampling with concentrations over three times higher than the other tributaries for the same event.

These results are consistent with rapid suburbanization and accompanying land use changes in these sub-watersheds.

 

Fall Creek Watershed Bee Branch (FCW1) Event Flow 7/07/03                Cicero Creek Watershed Hinkle Creek (CCW1) Event Flow 9/23/03

Conclusions

 This study suggests high concentrations of TKN and sediment (and associated phosphorus) are highest in spring season and runoff events.

Delivery of these nutrients into drinking water supply reservoirs may in part be responsible for triggering algal blooms and associated taste and odor causing compounds.

The monitoring of physical and chemical conditions in the watersheds throughout the year continues to provide critical information about seasonal loadings in the drinking water supply reservoirs and aids in the development of both reservoir and watershed management programs. Additional sampling is scheduled and is necessary to adequately characterize these complex systems.

Acknowledgements

Funding for this research was provided by USFilter. Special thanks to the staff of the USFilter Indianapolis Water labs for running the chemical analyses on water samples. We would also like to thank the Center for Urban Policy and the Environment at IUPUI for their land use assessment of the watersheds.

Publications\2003-GSA_Shrake.ppt
 

Shrake, L.K., Hall, B.E., Tedesco, L.P., Atekwana, E.A., Latimer, J.C., and Filippelli, G.M., 2003. Watershed Contribution to Three Central Indiana Reservoirs: Characterization of Suspended Sediment and Dissolved Loads. Geological Society of America Abstracts with Programs. 35(6): 144.

A viewer for this file can be found at the Microsoft downloads page

top of page