Tile Drainage - Social and Ecological Effects of Tile Drainage

Social and Ecological Effects of Tile Drainage

Unfortunately, the ability for farmers to install their own tile can be problematic. First of all, private installations may reduce the ability of local drainage supervisory boards to regulate tile installation, which in some areas of the country requires proper documentation before a contractor can continue. This leads to the second potential conflict, the unintentional interruption of existing tile networks. Most "do-it-yourself" tile plows do not dig trenches but rather split the soil enough to squeeze the tile line in; thus, a farmer would not be aware if he breaks a line of tile that might serve his neighbors, as well (Mutual tile lines are often dictated by topography rather than land ownership, and the location of many old, but still effective, tile lines are unknown.). The potential for across-the-fence disputes are obvious.

Ecologically, the expansion of drainage systems has had tremendous negative effects. Hundreds of thousands of wetland species experienced significant population declines as their habitat was increasingly fragmented and destroyed. Although market hunting within the Central Flyway was a contributing factor in the decline of many waterfowl species' numbers in the early decades of the twentieth century, loss of breeding habitat to agricultural expansion is certainly the most significant. Early maps of midwestern states depict many lakes and marshes that are either nonexistent or significantly reduced in area today. Channelization, a related process of concentrating and facilitating the flow of water from agricultural areas, also contributed to this degradation.

Tile drainage and the corresponding changes to the landscape - draining wetlands, wet soils, and channelizing streams - have contributed to more erosive rivers. This response of rivers due to drainage is the result of shortening the residence time of water on the landscape. For example, precipitation used to be held in wetlands and in/on the surface of soils, continuously evaporating or being used via transpiration of plants. Water would slowly drain through the landscape and eventually drain to rivers. The process of tile drainage, used to dry soils quickly and efficiently, results in an efficient transmission of water to the river - so efficient, in fact, that higher volumes of water are delivered to rivers. The effect of higher volumes of water is more energy in water - the dynamic equilibrium state that rivers existed in for centuries (slowly changing shape and continuously transporting limited sediment) was, and currently is, out of balance. The result of this loss of equilibrium is extreme amounts of bank erosion which results in over-burdensome sediment loads and critical impacts to natural environments and riverine habitats.

Drainage tile sometimes decreases soil erosion and runoff of some nutrients, including phosphorus. Phosphorus is an important nutrient to control because it is the limiting nutrient in most aquatic ecosystems. Thus phosphorus is the main culprit in eutrophication of surface water; however, the other limiting nutrient, nitrogen, causes substantial damage to waters. For example, nitrogen has been implicated in the gulf hypoxia. Drainage tile sometimes increases water quality because the water flows into the ground then the tile, instead of running off the field into a ditch, carrying soil and nutrients with it. The soil has a chance to filter the water before it enters the streams and rivers. However, tile drainage consistantly tends to be extremely high in nitrogent. Furthermore, some tile drainage sometime contains very high levels of other chemicals. In very flat areas, where the natural topography does not provide the gradient necessary for water flow, "agricultural wells" can be dug to provide tile lines sufficient outlet. In these cases, it is the groundwater that stands to be polluted by unfiltered tile output.

Intensive Livestock Operations (ILO) have led to challenges of livestock effluent disposal. Livestock effluent contains valuable nutrients, but the misapplication of these materials can lead to serious ecological problems, such as nutrient loading. Injecting effluent directly into the ground is one method employed by manure applicators to improve nutrient uptake. Drainage tiles may increase injected manure seepage into surface waterways from manure injection because liquid manure seeps through soils and then drains out of the field and into waterways via drainage tiles.

Today, a number of state and federal initiatives serve to reverse habitat loss. Many programs encourage and even reimburse farmers for interrupting the drainage of localized wetholes on their property, often by breaking tile intakes or removing the tile completely. Landowners are often partially or fully compensated for forfeiting the ability to grow crops on this land. Such programs and the cooperation of landowners across the country have had significant positive effects on the populations of a wide variety of waterfowl.