Usually a pattern exists, with increased numbers of people using the lake during holidays causing bacteria counts to rise and then drop off later in the week. Bacteria counts in Lake Havasu fluctuated erratically, even when population pressure was removed. During the intensive investigation period there were no spills nor excessive urban runoff in the area to account for the high bacteria count. Also puzzling to researchers is that the high bacteria counts at Lake Havasu were not accom panied by high nutrient values. Nutrient values in near-shore waters were low.
Work continues to locate the source or sources of the problem.
Researchers examined the theory that the high bacteria count might be the re sult of a natural process. Sampling therefore was done at other areas of Lake Havasu with conditions similar to the affected areas, but without the population pressure. High bacteria counts were not recorded. This led investigators to believe that there probably is a near-shore source of the problem. Continuing research will include a study of groundwater transport on an island near the affected beach areas, including transport from a wastewater treatment plant with a recharge pond.