Focus
Sun Lakes water quality study results

Introduction

The Washington State Department of Ecology has just released a study of the Sun Lakes called the "Sun Lakes Trophic Status Assessment Study." The research was aimed at better understanding the effects of increased human-caused pollution on this popular chain of lakes.

Background

Residential and recreational use of the Sun Lakes, in the lower Grand Coulee area between the towns of Coulee City and Soap Lake, has increased substantially in recent years. The area attracts almost a million visitors each year. The Sun Lakes area boasts the Lenore Lake Wildlife Area, several resorts, and Sun Lakes State Park. Information about the quality of the water in these lakes is currently inadequate. Because of this, The Washington State Department of Ecology launched a study in the spring of 1996 to get to know the status of the quality of water in the lakes. Ecology needed to fill the gaps in its scientific knowledge about Deep, Park, Blue, Alkali and Lenore lakes-the five largest lakes in the chain. Having this information would be an important first step toward ensuring that the lakes remain attractive and clean for future use. (Soap Lake was not included in this study because more is already known about Soap Lake.)

Study Goals

One goal of the study was to find out what effect "nutrient loading" is having on the lakes. Nutrient loading is when compounds from waste and fertilizers, such as nitrogen and phosphorus, enter the water. This can happen when sewage is managed poorly, when animal waste enters the lake, or when fertilizers from residential and agricultural runoff wash into the lake.

Excessive nutrients can cause serious problems for lakes because they fuel the growth of algae (which can result in a "pea soup" appearance) and are responsible for the subsequent loss of oxygen when the algae die and decompose. This can all affect the lake as a fishery resource and can cause aesthetic and public health problems. Another goal of the study was to assure that we have basic information about the water quality of the lakes so that in future years we can see how the quality of the water changes. A third goal is to evaluate the potential damage that increased human activity in and around the lakes may have on water quality.

Conducting the study

Samples at each of the five lakes were collected and analyzed each month from May to October 1996. Scientists also collected samples from various depths of each lake. The samples were analyzed at Ecology's environmental laboratory. The scientists also used meters to measure temperature, oxygen, and other qualities that tell about the health of the water. One meter was attached to a cable and used to take measurements from the bottom to the top of the lake, while others were moored in one place for several days to measure the changes from day to night. In addition, scientists monitored creeks between the lakes, springs feeding the lakes, and surveyed aquatic plants.

Study results and recommendations

Deep Lake is a beautiful, pristine lake, but the state park and its visitors will need to work to keep it that way. Both Park Lake and Blue Lake are heavily used and show the effects of nutrient loading. Because they are at the downstream end of the system, Alkali and Lenore lakes both need special attention if they are to remain attractive and healthy. Ecology recommends that water quality monitoring continue and that a lake association be formed to share information, educate each other about lake water quality, and implement water quality improvement recommendations.

Ecology also recommends that wastewater should be properly managed to prevent serious water-quality problems. The report supports the lining of wastewater lagoons at parks and resorts, and education of visitors on proper wastewater disposal.Other recommendations in the report include keeping livestock away from the water and managing fertilizer use carefully. The report concludes, "Poor management of nutrient sources could threaten the ability of these lakes to support high-quality recreation."