The InWMC is proud to highlight the work that the Louisville District US Army Corps of Engineers Water Quality Team has done in performing 2017 Biological Assessments of Brookville and Cecil M. Harden Reservoirs. The Water Quality Team’s objectives for these assessments were to measure water quality condition of inflows and outflows of target reservoirs, assess for compliance with state criteria in tail waters, and use results to inform water management decisions. Zachary L. Wolf, US Army Corps of Engineers Biologist, summarized the Biological Assessments of Brookville and Cecil M. Harden Reservoirs by saying,
“The Louisville District US Army Corps of Engineers Water Quality Team assessed the watersheds of Brookville and Cecil M. Harden reservoirs in Indiana by analyzing the biological community in major tributaries to the reservoirs and their respective tailwaters. Benthic macroinvertebrates and fish communities were collected and analyzed following methods used by the Indiana Department of Environmental Management (IDEM) in 2017. This includes the Macroinvertebrate Index of Biotic Integrity (mIBI) and the fish community Index of Biotic Integrity (IBI), which each have ratings of Excellent, Good, Fair, Poor, and Very Poor.
For the Brookville Reservoir watershed, mIBI ratings were either Fair (82%) or Poor (18%) and IBI ratings were either Good (18%), Fair (73%), or Poor (9%). The average mIBI was 36.2 (range: 24-40) and the average IBI was 43.1 (range: 34-52), which would both have a rating of Fair. These results suggest the watershed has some level of impact from human disturbance but still has fair stream health, with the exception of the tailwater. The tailwater had the lowest score for mIBI and IBI and was the only location with two Poor ratings, indicating poor stream health.
For the Harden Reservoir watershed, mIBI ratings were either Good (33%), Fair (33%), or Poor (33%), and IBI ratings were either Good (33%) or Fair (67%). The average mIBI was 38.7 (range: 28-46) and the average IBI was 41.7 (range: 38-46), which would both have a rating of Fair. These results suggest the watershed has some level of impact from human disturbance but overall has fair stream health. Although the tailwater had a Poor mIBI rating, the tailwater IBI rating was Good, indicating the tailwater may have a healthy fish community but could benefit from improvements that mitigate impacts to the macroinvertebrate community.
The results of our biological assessments provide valuable information of the health of the watersheds of these reservoirs, including the health of the aquatic community of their respective tailwaters. This information can be used in determining the impacts of current dam operations on the biological community in the tailwater and the water quality flowing into the reservoirs from major tributaries. This will be applied in determining best management practices of the dam and to the long-term monitoring of these reservoirs and their watersheds.”
More information can be found by visiting http://www.lrl.usace.army.mil/Missions/Civil-Works/Water-Information/Water-Quality/ or emailing louisvillewaterquality@usace.army.mil.
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Photos and images for this post were provided by the Louisville District US Army Corps of Engineers Water Quality Team.