Species-Richness Responses to Water-Withdrawal Scenarios and Minimum Flow Levels: Evaluating Presumptive Standards in the Tennessee and Cumberland River Basins

Water-resource managers are challenged to balance growing water demand with protecting aquatic ecosystems and biodiversity. Management decisions can benefit from improved understanding of water-withdrawal impacts on hydrologic regimes and ecological assemblages. This study used ecological limit functions for fish groups within the Tennessee and Cumberland River basins to predict species richness responses under simulated constant-rate (CR) and percent-of-flow (POF) withdrawals and for different minimum flow level protections. Streamflow characteristics (SFC) and richness were generally less sensitive to POF withdrawals than CR withdrawals among sites, fish groups, and ecoregions. Species richness generally declined with increasing withdrawals, but responses were variable depending on site-specific departures of SFCs from reference conditions, drainage area, fish group, ecoregion, and minimum flow level. Under POF withdrawals, 10% and 20% daily flow reductions often resulted in loss of <1 species and/or ≤5% richness among fish groups. Median ecological withdrawal thresholds ranged from 3.5–31% for POF withdrawals and from 0.01–0.92 m3/s for CR withdrawals across fish groups and ecoregions. Application of minimum flow level cutoffs often resulted in damping effects on SFC and richness responses, indicating that protection of low streamflows may mitigate hydrologic alteration and fish species richness loss related to water withdrawals. Site-specific and regionally summarized responses of flow regimes and fish assemblages under alternative withdrawal strategies in this study may be useful in informing water-management decisions regarding streamflow allocation and maintaining ecological flows.

“Supposed to be Spys”

This chapter focuses on the suspicions surrounding the two African fugitives that Ira P. Nash and Jefferson sought to help. In October 1807, Jefferson sought a translator, discreetly circulating two Arabic manuscripts on the East coast. Out West, it was not outlandish writings, but strange rumors, that were reportedly circulating. These whispers, unlike the President’s search, were unsympathetic. From Washington, the African captives appeared unduly incarcerated, “confined, on suspicion, merely,” in Jefferson’s words. On the frontier, however, “suspicion” was not so easily dismissed. Racial prejudice had initially halted the two Muslim fugitives in the spring; by the autumn, it was not bias, but apprehensions that seemed to be rising on the Cumberland River. The two Africans, whose “business” remained unknown, appeared to “some” not as escapees, but agents of espionage.