Toronto Lake: Water Quality Status Fact Sheet

Location Siltation Toronto Lake is a 2,800 acre lake, along with siltation and dissolved Toronto Lake has high inorganic located in the scenic Flint Hills oxygen deficiencies encompass the and high levels of siltation. region of Kansas with a maximum primary water-quality problems in The lake is shallow and is depth of approximately 5.5 m and a Toronto Lake. re-suspended easily due to wind, mean depth of 2.1 m. Construction motorboat traffic, and moderate to was completed by the Tulsa District high inflow events. Siltation is Corps of Engineers in 1960 by Though eutrophication occurs aggravated during large runoff events damming the Verdigris River and naturally, it can be accelerated when releases from Toronto Lake are Walnut Creek to control flooding. through an anthropogenic process minimized to accommodate flood that causes reservoirs to become control along the Verdigris River, Land Use more productive or eutrophic due to which causes large deposits Toronto Lake lies within a 690-sq. excessive nutrient additions from within the lake and the inflowing mile watershed that is predominantly their associated watersheds. river channels. Subsequent runoff grassland (70%). Pasture/hay events of moderate duration then occupies 15% of the watershed, The chlorophyll a (Chla) facilitate the transport of that while forest accounts for 5% and concentration has been used as a deposited sediment into the lake cropland 4% of the total land area general trophic indicator of a where it may settle out. within the watershed. waterbody. Toronto Lake averages 14.9 µg/L of Chla, which ranks as the Dissolved Oxygen Water Quality’s Decline 13th highest in the state among the Dissolved Oxygen concentrations Toronto Lake is a Class A primary federal reservoirs. The occurrence of significantly drop around the 4-meter contact recreational water for public low Chla concentrations is closely depth range in Toronto Lake. swimming. Other designated uses associated with low water clarity (or Temperature readings are generally include aquatic life support, food high turbidity) conditions. High stable throughout the , procurement, drinking water, ground turbidity, caused by suspended indicating that the lake is not water recharge, industrial water particles, negatively affects stratified. Low dissolved oxygen supply, irrigation use and livestock communities and light concentrations are likely prevalent watering use. penetration. when the lake is turbid and temperatures are warmer. The KDHE water quality data collected Toronto Lake - Chlorophyll a Data for Main Basin decomposition of plant material has from 1992 to 2007 revealed that 22 lowered the dissolved oxygen Toronto Lake ranks as the ninth 20 18 concentrations toward the lake highest for total phosphorus (TP) 16 14 bottom.

12 concentration of the 24 federal Dissolved Oxygen Average Concentrations in Toronto Lake 10

8 reservoirs in the state. TP Chl-a (ug/L) 8 6 7 concentrations range between 55-108 4 2 6 µg/L, with an average concentration 0 5

of 81 µg/L, which is ~4 times greater 1975 1978 1981 1986 1989 1992 1995 1998 2001 2004 2007 4 Year DO in mg/L than the statewide benchmark of 23 3 µg/L. 2 The average total nitrogen 1 concentration within Toronto Lake is 0 The total suspended solids (TSS) 1975 1978 1981 1986 1989 1995 1998 2001 2004 2007 0.64 mg/L. Toronto Lake is Average concentration, indicative Sample Year generally limited by light and DO Avg from 0-3m DO avg. 2-3m of turbid conditions, is high and nitrogen. However, during the years averages about 30 mg/L, third with the higher chlorophyll a Community highest among the federal reservoirs. concentrations (1995, 1998, and Toronto Lake offers sports-fishing Because of the appearance of high 2007) the lake was co-limited by opportunities throughout the year and turbidity values, the lake has low light, nitrogen and phosphorus. is known for having “an abundance water clarity with an average secchi of some of the largest white bass in depth value of 35 cm. Eutrophication the world” (USACE). According to

the Kansas Department of Wildlife and Parks fish survey, the number of oxygen should exceed 5 mg/L for the rate at 96,300 adult fish Captured Per Unit Time entire water column of the lake. The tons/year of TSS (sediment) Effort (CPUE) shows that white bass model results concluded that the total accumulating on the bottom of the have been increasing, largemouth phosphorus and total nitrogen lake each year and the TMDL for bass fluctuate from year to year and concentrations entering the lake from TSS is set at 55,854 tons/year based white crappie have remained both Walnut Creek and the Verdigris on a regression calculation. somewhat stable. Bottom feeding River must be reduced by 30% to Therefore a 42% TSS reduction is fish are dominated by variable achieve the necessary load reductions necessary to achieve a secchi depth gizzard shad populations and channel for the lake. of 0.7 m. catfish have been stable.

Runoff Potential Parameter Current Avg. TMDL Percent Reduction Runoff plays an important role in Condition transporting nutrients and sediment TP Annual Load (lbs/year) 71,686 50,585 29.4% TP Daily Load (lbs/day)* 373.2 263.3 29.4% to the lake. It occurs as precipitation TN Annual Load 691,437 490,450 29.1% is greater than soil permeability. (lbs/year) According to the Natural Resources TN Daily Load (lbs/day)* 5077 3601 29.1% Conservation Service’s soil database TP Main Basin (µg/L) 73.0 52.4 28% (STATSGO), the soils in the TN Main Basin (µg/L) 636.0 492.3 23% watershed have low permeability Secchi Depth (m) 0.4 > 0.70 75% Increase

values. Eighty-one percent of the Sources Priorities soils have permeability < 0.56˝/hr. The watershed-average soil Nonpoint sources are the main In general the areas that should be permeability is 0.43˝/hr. contributor for the nutrient input and targeted for implementation include impairment in Toronto Lake. Runoff the HUC12 subwatersheds along the Restoration of Toronto Lake transporting nutrient loads associated main stem of Walnut Creek, and the Based on the Clean Water Act, a with animal wastes and cultivated Verdigris River in addition to the waterbody that does not meet water crops where fertilizer has been subwatersheds adjacent to the lake quality standards is considered applied contribute to the eutrophic “impaired”. The Clean Water Act condition of the lake. Load TSS Load TSS tons/year TSS tons/day* requires states to develop a clean-up allocations within the TMDL Wasteload Allocation 21 0.1 plan for all impairments. The clean- resulting from nonpoint sources for Load Allocation 50248 261.5 up plan and the process used to phosphorus and nitrogen are 43,913 Margin of Safety 5585 29.1 develop it is the Total Maximum lbs/year and 419,868 lbs/year TSS TMDL 55854 290.7

Daily Load (TMDL). A TMDL for respectively. Wasteload allocations Toronto Lake was developed to associated with point sources total Implementation of Watershed address eutrophication, siltation, and 1,383 lbs/year and 6,289 lbs/year for Management in Reducing dissolved oxygen in 2007. phosphorus and nitrogen Phosphorus Entering the Lake respectively. Point sources attribute To abate excessive phosphorus and The TMDL provides allocations for to less than 3% of the total sediment, here are several phosphorus (TP), nitrogen, and total allocations for phosphorus and recommended agricultural practices: suspended solids (TSS) loads. A nitrogen. The discharging point (1) Apply nutrient best management lake model (BATHTUB) was utilized sources in the watershed include the practices (BMPs) to reduce nutrient to determine phosphorus and Cities of Toronto, Hamilton, and additions from excess fertilization; nitrogen allocations to the lake. In Madison. (2) Promote and adopt continuous order to improve the trophic no-till cultivation to minimize soil condition of Toronto Lake from its Siltation loading comes erosion and nutrient transports; (3) fully eutrophic status, the desired predominantly from nonpoint source Install grass buffer strips along streams; (4) Reduce activities within endpoint of the TMDL is to maintain pollution as well. Overland runoff the summer chlorophyll a can easily carry sediment to the riparian areas; (5) Setback both concentration below 10 µg/L. In stream segments and eventually to confined and non-confined animal feeding operation sites; and (6) order to improve the clarity of the the lake. The level of the siltation water column and the siltation impairment can be measured through Construct /detention basins, impairment, the endpoint should also secchi depth readings, which can be erosion control structures and/or result in an increase in the average improved through setting allocations to reduce and to transparency of the lake to 0.7 and reductions for total suspended trap sediment and lower peak runoff meters, as measured by the secchi solids (TSS) for Toronto Lake. The rates. disk depth within the main basin of TMDL calculated the current the lake. In addition dissolved

Watershed Planning & TMDL Section, Bureau of Water, Kansas Department of Health and Environment 1000 SW Jackson Street, Suite 420, Topeka, KS 66612; website http://www.kdheks.gov/tmdl/index.htm