Why should I care about watershed?
Clean water matters to all of us! We depend on water for drinking, recreation and irrigation. Fish and wildlife depend on clean water. In Minnesota, fishing and hunting, plus other water-based recreation, are an important part of our economy. Studies have shown that water clarity is linked to property values: as water clarity declines, so does the value of the properties surrounding a body of water.
How does all this relate to watersheds? The water quality of lakes and rivers is affected by activities upstream or upland of the waterbody within the watershed so it is important to know the geographic area encompassed by the watershed surrounding your lake, river or stream. Especially important are the watershed processes that affect how water, sediment, and other materials get transported downstream. Looking at both natural processes and human influences from a watershed perspective is vital for dealing with concerns such as lakes that are unsafe for swimming or declining fish stocks.
Actions on the land, impacts in the water
Water moves through a watershed according to the hydrologic cycle. Water on the surface of the land can either flow downstream through the watershed, soak into the ground, evaporate into the atmosphere, or it can be taken up and used by plants or animals. Human impacts to that process can change the water quality (how clean it is), the water quantity (how much there is), or the timing (when it moves through, especially seasonally).
As an example, imagine that Hypothetical Lake is suffering from declining water clarity. Data collection shows that too much sediment is coming into the lake. To decrease the amount of sediment, resource managers must consider what is happening upstream in the river that runs through the lake. Likewise, they must also consider what land uses upstream might be allowing excess sediment to get into the river. Everything happening upstream in Hypothetical Lakes' watershed can have an impact on the lake. In most cases, however, the land uses in neighboring watersheds won't have an impact on Hypothetical Lake.
What are the sources of water to lakes and streams?
Water runs over land surfaces (overland flow) and into stream channels when it rains, when snow melts, or during irrigation. Water also seeps into and through the soil and underground (groundwater flow). Groundwater does not necessarily always follow the same watershed boundaries as surface water. In fact, groundwater flowing into lakes can sometimes originate from outside the watershed. Plants intercept water on their leaves and take up water from the soil. Land uses can alter the natural flows of water. Impervious surfaces such as parking lots, roads, and rooftops increase the speed and amount of stormwater flow into lakes and rivers.