This project aims to provide the client, the Huron River Watershed Council (HRWC), with a framework for assessing flow alteration and its impact on the biological community of the Huron River. We conducted analysis on annual, monthly, daily and sub-daily hydrological data, precipitation, land cover change, fish and benthic invertebrate communities in the watershed.
Most hydrologic parameters concerning flow volume demonstrate an upward or non-changing pattern for the recent 100 years. The base flow gradually increases, while the reversal number gradually decreases, suggesting a more stable flow regime. In terms of daily and sub-daily flow regime, the gage near Ann Arbor sees the largest flashiness among all gages, which could be the result of dam regulation in the upstream region.
We found a strong correlation between precipitation and flow discharge, and an increasing trend in precipitation similar to the trend of flow discharge, while the runoff coefficient did not change significantly over time. This result implies that the increase in precipitation due to climate change is a major driver of the flow increase. With the current climate change trend, we expect to see even more water in the river.
Increase of urban/impervious land is the major land cover change in the watershed, which results in more runoff in rainfall events and lead to higher flashiness of the river. Urbanization also has a negative impact on stream habitats for benthic macroinvertebrates as the input of fine substrate and pollutants rises.
Fish assemblages at sample sites along the river were compared by their preferences for: water temperature, stream size, substrate type, etc. The most defined trend resulted from the comparison of riverine versus impoundment habitats. In impoundment environments, a higher percentage of the sample population exhibited the following characteristics: game fish, tolerant species, preference for large size streams, substrate generalists, preference for slow flowing water, and piscivore trophic guild. Conversely, in riverine environments, a higher percentage of the sample population exhibited the following characteristics: darters, intolerant species, rock or gravel substrate preference, preference for medium flowing water, and insectivore trophic guild.
A Habitat Suitability Model was used to predict expected fish communities at a given site, and to compare expected fish communities to sampled fish communities in the Huron River main stem. Preferred and suitable flow ranges for various species and communities were calculated for sites within the Huron River. Fish communities around Ann Arbor and Ypsilanti are not representative of model communities for the river type, temperature, and size. Present fish communities prefer a flow range with a significantly higher upper bound relative to model the communities in Ann Arbor and Ypsilanti sites. An Adverse Resource Impact occurs in Ann Arbor at a low flow of around 45 cfs and in Ypsilanti at around 51 cfs. Ann Arbor has the highest amount of historic ARI occurrences throughout the Huron River indicating that it is necessary to prioritize associated dam operations. Using this model, an Ideal and suitable flow range can be determined for desired fish communities for each reach of interest.
- Zhenyue Duan, MS Environmental Informatics
- Chuck McDowell, MS Conservation Ecology
- V.M. Summer Roberts, MS Conservation Ecology
- Yu-Chen Wang, MS Environmental Informatics
- Xin Xu, MS Conservation Ecology