Watershed area for Wawasee and Syracuse

Questions about Lake Wawasee and Syracuse Lake water levels have been among the most common research-related questions received by the Center for Lakes & Streams over the past few years.

In 2012 the lake levels in Wawasee and Syracuse dropped about 18 inches below normal. The expanded study evaluated the causes of lake level changes during normal years of 2011 and 2013 and the drought year of 2012. A lake water budget and watershed budget was developed focusing on inflows and outflows directly to and from the lake and the entire drainage area.

A preliminary technical report was provided in late 2013. Since then, the study was expanded based on feedback from those around the lake to include 2011-2013 data as well as more residential, golf course and agricultural irrigation information.

The conclusion: the main causes of the changing lake levels are uncontrollable factors. The report, by the Center for Lakes & Streams, determined lake managers and property owners cannot control the amount of water entering the lakes from rainfall, groundwater and streams. Neither can there be control over evaporation.

The study did determine there is control over lake levels through dam operations. The Syracuse dam helps control levels when water is able to go over the spillway, but once levels fall below the spillway, the dam cannot help. Lake property owners can also control lake water loss with residential irrigation systems.

The study suggest for future droughts it may be effective to limit irrigation systems. Expansion of agriculture irrigation systems is something to monitor. The current study found irrigation systems were not as influential as first thought, but still impact the lake..

This study took into consideration of water entering the lakes through precipitation, streams and groundwater (springs) and leaving the lakes through evaporation, Syracuse dam and irrigation being taken directly from the lakes.

Precipitation in 2012 was about half the amount of 2011. This decrease also affected inflowing streams. Because of low rainfall, the streams delivered less than half of the water in 2012, than 2011. Though there was an increase in groundwater flowing into the lakes in 2012, compensating for some decreases, the total inflow still decreased from 2011 to 2012.

The study found lake outflows also changed. Evaporation increased in 2012 due to warmer temperatures. Water leaving through the dam decreased from 2011 to 2012 because once the water level fell below the spillway, the dam did not release any more water. While 60 percent of all water leaving the lakes in 2011 left through the dam, only 30 percent of all water leaving in 2012 was through the dam. Residential irrigation accounted for 2 percent in 2011, but increased to 3 percent in 2012.

The result was less water entering and more leaving the lake in 2012, resulting in extremely low lake levels.

Watershed Water Budget

At the watershed level changes in groundwater are changes in aquifer storage and were not used in calculating the budget, but included as reference.

In 2011, 33.3 million cubic metre or m3 of water was transferred into the aquifer under the surface, in 2012 the aquifer lost 6.5 million m3 of water. In 2011, there was enough precipitation and stream flow in the watershed to allow water to soak into the ground and into the aquifer. During 2012, less water was coming into the watershed from rainfall even while exapotranspiration and dam outlet losses continued, not allowing the aquifer to recharge.

Significant wells in the watershed were included in the study, especially due to interest in agricultural wells. The total amount of water taken out of the aquifer by the wells were almost 1 million m3 of water in 2011, accounting for about 1 percent of precipitation inputs. In 2012, there was an increase of 1.4 million m3 taken by the wells, accounting for 2 percent of the precipitation.

The report states the hypothetical addition of 20 new agricultural wells, in addition to the 17 already in the watershed also quantified for reference. The largest agricultural well was selected and with projecting the addition of 20 more wells pumping at the same maximum rate. An additional 8 million m3 of water would be taken out of the aquifer per year on average under these conditions. Combined with the existing wells, this would account for about 10 percent of annual precipitation. This increase in agriculture irrigation would be relatively small compared to the total watershed budget in a normal year, but could exacerbate low water levels like residential irrigation during drought years.

The study suggests expansion of agricultural irrigation systems is something to monitor.

Study information was compiled by Dr. Nathan Bosch, Joellyn Moine, Margaret Lee and Anna Burke

To see details of data collected click: Lakes & Streams Tables