Dead Fish at Sweetwater Reservoir

By Neil Ray

August 6, 2004

Some may have noticed the recent accumulation of several species of dead fish at Sweetwater Reservoir. Several thousand fish are scattered among the bank of the lake. It is unclear to the exact cause of such an adverse turn to the lake’s ecosystem. There are several theories that come to mind. Some lakes such as Sweetwater undergo a natural process twice a year, where the lakes turn over. This usually occurs during the winter and summer seasons. During the winter, warmer water that is rich is nutrients, is circulated to the lake bottom and colder water is placed on top. The summer season is an opposite process where warmer water is placed on top. Last two years of draught conditions, which have brought Sweetwater’s water level to approximately five feet may have fatally altered the lakes process of turning over. This can cause anoxic conditions, which means the lake is lacking a suitable amount of oxygen for the fish to survive. However, several other theories are more plausible, as fish can bury themselves in the mud to avoid the intense heat and thrive on nutrients on the lake’s bottom for an extended period of time.

A more plausible theory is that pollutants entered the reservoir either by surface runoff or groundwater flow and contaminated the lake. Chemicals need not be dumped directly into the reservoir to have adverse effects on the watershed. If chemicals are dumped into the ground nearby they may enter the water table, which can enter Sweetwater by a groundwater recharge process known as base flow, which is the natural means of recharging the lake. Several factors effect water quality such as concentration of the chemical that was dumped, where it was dumped, and the nature of the solution.

Chemicals react differently to the soil by several properties. One such property is porosity, which is how much pore space is available for the liquid to travel through. Most of the soil in Kiowa County is known as Loess, which is wind blown sand. Loess has a high porosity so liquid can travel at relatively high speeds through sandy sediment. But, perhaps one of the most important properties to consider is the nature of the pollutant. The type of contaminant will determine exactly how fast it reaches the water table. This property is known as viscosity, which is resistance to flow. For example, molasses is highly resistant to flow so it is said to be viscous, whereas vegetable oil will flow much faster so it is less viscous. There are various other properties that are much too numerous to mention in the scope of this article, but one should consider the effects of water pollution. Farmers should be cautious as to the type of pesticide they are using and the concentration.

Not only is it considered a serious crime to pollute our water, but also an unethical one. Remember that everyone has to drink the water that comes from our natural aquifer system, whether or not you have a private well or city water. The important factor to consider is that we should preserve our natural resources considerably, especially our natural watersheds. The reservoirs of Kiowa County are both recreational for the sports enthusiast and a necessity. In the event of suspected contamination, my opinion as a geologist would be to establish a steady groundwater quality monitoring system in close consideration with the Environmental Protection Agency, in an effort to clean up Sweetwater. In such a case contaminants may continue to spread as a plume, following the elevation of the water table, and further contaminate other water resources nearby. Grants available to Kiowa County by the EPA, may significantly reduce costs that the county would have to pay for such a project. Although it is unclear as to what caused the event, further investigation needs to be taken.