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Aerial view of Houghton Lake, looking northeast. The red line marks the  boundary of the Conservancy's acquisition. The dotted blue lines represent the tiles and major ditches, which currently drain water away from the lake and wetlands. Photo © Rich Fields, Indiana DNR Restoration of Houghton Lake The Nature Conservancy's restoration goals for Houghton Lake are deceptively simple. To the maximum extent possible, we want to restore groundwater flow and quality to the lake and wetlands. To accomplish this we will have to remove buried tiles from the agricultural fields and fill in many of the ditches that currently intercept groundwater before it discharges to the lake. This will move more water through the lake itself, which will help to flush out chemicals and nutrients from adjacent farmfields that have accumulated over the decades. The lake currently has an annual flush of algae which should decrease as nutrients leach out of the system over the years. This will improve habitat for native fish, amphibians and reptiles as the water clears over time. There is one disruption that we will not restore: the natural lake water level. Although the outlet of the lake is man-made and has dropped the lake several feet, we will not manipulate it. The wetland habitats that have developed on the exposed lake bottom are too valuable and it would be foolish to drown out  these high-quality habitats. The adjacent fields will be restored to appropriate native wetland and grassland communities. The hydrologic restoration will create very wet muck soils in the valley bottom, which we hope to restore to sedge meadows, wet prairies and fen communities. This will increase habitat for many wetland species, especially rare snakes and turtles at the site. The rolling uplands will be planted to prairie to reduce agricultural runoff to the wetlands and to create additional habitat.

Great Blue Heron
Photo © Tom Gross

Houghton Lake

A Rare Opportunity

Houghton Lake in Marshall County is a wonderful example of a highly alkaline natural lake. It lies at the bottom of a broad valley that likely once carried off massive quantities of glacial meltwater. The lake is primarily fed by groundwater discharges from the surrounding hills of rolling glacial till. As water seeps through the till, it picks up a heavy load of dissolved limestone, which then precipitates out as marl (a lime rich mud containing variable amounts of clays and calcite; the term is most often used to describe lake sediments.) in the valley bottom. The bottom of Houghton Lake and its shoreline are cement-gray, the color of deep marl deposits. The surrounding wetlands reflect this as well. Extensive fens at Houghton Lake are a mixture of alkaline peat (an accumulation of partially decayed vegetation matter, formed in wetlands) and, nearer the lake, pure marl.

But by no means is Houghton Lake a perfect system. As with most of Indiana, the tillable lands that surround the lake are in agricultural production. Many of those agricultural fields were once fens. Ditches and tiles move water out of the fields and away from our wetlands and the lake. And invasive species are as abundant here as they are elsewhere in the state. One of the worst is common buckthorn, which out-competes native plants for nutrients, light, and moisture and degrades wildlife habitat.

What remains so remarkable for Indiana, is the fact that an entire site, all 360.63 acres, was purchased as a single unit. Unlike most conservation areas where we and our partners work piecemeal, the lake and surrounding wetlands were located in the heart of a family-owned farm that was on the market. With a decisive stroke, we were able to purchase the half of the farm that included the 100+ acres of high-quality lands that included the lake and all the surrounding wetlands. We also acquired around 90 acres of lower-quality natural lands that include old marl pits, second growth forests and a very interesting small glacial outwash rise that supports about 5 acres of overgrown oak savanna. Once restored to more open savanna conditions and managed with fire, the sand and gravel soils on this small rise will provide important nesting and foraging habitat for turtles and snakes that currently have limited opportunities to lay their eggs near the wetlands.

But perhaps most importantly for the long-term, we control almost 180 acres of agricultural fields that surround the site. These include a mix of rolling hills that drain agricultural runoff towards the lake, as well as tiled muck fields that were once part of the wetlands themselves. These are the lands that have the most impact on the future of the site and the rich variety of species it supports. The agricultural drainage system is obviously designed to pull water from adjacent muck soils. This decreases the extent of the wetland complex, but also diverts the flow of groundwater away from the lake. Many of the ditches cut deeply into the perimeter of the natural area, creating fens that seem unnaturally dry. The lake itself is much lower than it once was because of this drainage. Much of the fen, including portions that grow on heavy marl soil, is on recently exposed lake bottom. Lowering the water table has helped problematic species as well, allowing both native and non-native aggressive species to become well-established on ditch spoils and field edges. The future of this preserve depends on our successful restoration of the adjacent fields over the next few years.

This is a complex task. It will take us at least two years just to get ready to start the restoration. Reed canary grass, another invasive species that thrives in disturbed areas, will have to be eliminated from the ditch and field edges before we can begin. Likewise, native cottonwood trees line the ditches and shower the landscape with millions of seeds annually. As we have learned at our Kankakee Sands project, cottonwood seedlings can turn open restorations into dense thickets if they become established. We have already begun the arduous task of removing cottonwoods from the field and ditch edges. In the meantime, as we prepare the site for restoration, we will continue to farm in order to keep our fields relatively weed free.

As straightforward as the Houghton Lake acquisition was, the restoration of this “opportunity of a lifetime” will be a very involved process. To really conserve this amazing natural area will require two years of planning and preparation; a few months of earth moving and planting; and at least a decade of intensive follow-up management. 

We encourage you to follow our progress at this important site.