Temporal variability of two contrasting transient pollution events in a pastoral stream.
Two transient pollution events were monitored in a pastoral stream in southwestern Kenya to evaluate their relative contribution to diffuse pollution. Peak loads of pollutants during storm-induced transients were within 3-4 orders of magnitude higher than the short-lived (30-60 minutes) diurnal episodes provoked by in-stream activities of people and livestock. Transient yields were striking during storm-induced events; 778,000, 8,400, 550 and 100 kg day(-1) for suspended solids, BOD(5), total P and total N, respectively, compared to wet weather base flow (150, 30, 0.8 and 1.4 kg day(-1), for the same parameters, respectively). Two forms of concentration-discharge relationships were observed: increases in concentration for turbidity, suspended solids, BOD(5), total P and the faecal indicator bacteria at the peak of the stream hydrograph, and concurrent decreases in concentration for conductivity and total N. Following each storm-induced transient event, a marked improvement in water quality was observed within 48-72 hrs of the receding limb of the stream hydrograph before the next base low was established. It was concluded that storm-induced transients are exceedingly important for the mobilization of pollutants from diffuse sources but both transient events affect stream-channel processes, especially water quality, with the possibility of attendant consequences on the health of riparian inhabitants.
Yillia
P T
PT
Vienna University of Technology, Institute for Water Quality, Resources and Waste Management, Karlsplatz 13/226, Vienna, Austria. pyillia@iwag.tuwien.ac.at
Kreuzinger
N
N
Mwetu
K K
KK
D004784:Environmental Monitoring / Q000379:methods; D004787:Environmental Pollution; D005618:Fresh Water; D005843:Geography; D019015:Geologic Sediments; D007630:Kenya; D011891:Rain; D013997:Time Factors; D014871:Water Microbiology; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D014881:Water Supply; D014887:Weather
D014874:Water Pollutants, Chemical