Data for three rivers in the upper Sevem catchment are examined to assess the influence of regulation strategies on the thermal characteristics. Seasonal and die1 temperature variations are markedly influence by the release discharge and the depth of withdrawal from the reservoir. The downstream influence of river regulation is confined to a relatively short reach (ca. 30 km) below the dams. Nevertheless, the control of water temperature during hot, dry summers could benefit salmon populations.
A human-impacted watershed was monitored during the dry summer seasons in 2002 and 2003 to investigate the impact of providing access to sewer mains to local village residences. Faecal coliform concentrations were monitored at select sites along the 30-mile stretch of creek, together with faecal streptococci, enterococci and total coliforms. Analysis of the results found that levels of faecal coliforms were inadequate at identifying significant known influxes of human and animal sewage established by sanitary survey. However, the bacterial ratio of atypical colonies to total coliform colonies (AC/TC), obtained from the total coliform membrane filter assay on m-Endo media, correctly indexed human faecal impact of inadequately sewered villages located along the creek. In addition, the AC/TC ratio correctly classified the predominant source of faecal runoff in the creek headwaters as agricultural, and indicated when aged agricultural faecal material was introduced by tributaries. An approach for watershed management that uses the AC/TC ratio in addition to levels of bacteria is proposed.
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