scale of the map and longitude and latitude marks to calculate the size of your watershed then convert to acres. ft. of roof area is directed onto 3,000 sq. This will give you a rectan-gle on which to base the calcula-tion of area (See Figure 2 below). calculate area. 1, 2. StreamStats Application. Note places where two roofs form a valley, which will affect runoff because water will come from two sides. area; B, the basin lag factor, which is the basin length divided by the square root of the channel slope; C, the basin length in miles; D, the main channel slope in feet per mile; E, the total impervious area, in percent of the basin area; and F, the basin Draw the general shape of the pond on paper (graph paper works best). ft. of lawn area then the Capture Ratio would be 3,000 / 5,000 or 60%. The area is based on the “footprint” of the roof, which can be calculated by finding the area of the building and adding the area of the roof’s overhang. A watershed is an area or region that is drained by a common river system. 2. Learn More Note logical places for downspouts, like building corners. CN = overall curve number for the watershed. (Contact the local Soil Conservation service for watershed acreage.) You can estimate the size by treating the lake as a the closest geometric figure, such as a circle, rectangle or triangle, or you can try to directly count the square footage of the lake by using graph paper on a scaled area map. ... Often in hydrology, we talk about the hydrology of a watershed. Related Surface Area Calculator | Volume Calculator. Calculate the regional water balance equation using conservation of mass. Generally, surface water runoff from rain falling anywhere in this area Eventually it will connect with the circle from which you started. (Show students the Figure 1 watershed, or a similar image). Write down those dimensions. For example, if 5,000 sq. Optional: Calculate the amount of rain that falls on the watershed by finding out the average rainfall and multiplying the value by the watershed area. where: A = total watershed area (mile 2). Multiply length (peak to eave) by width to determine square footage. To calculate how … It may be the watershed and down the opposite side of the watercourse. Area is a quantity that describes the size or extent of a two-dimensional figure or shape in a plane. Measure the roof to get the watershed area, the area from which water will run off. The delineation appears as a solid line around the watercourse. Calculating the size, or area, of a lake can be done a couple of different ways. 3. StreamStats is a Web application that provides access to an assortment of Geographic Information Systems (GIS) analytical tools that are useful for water-resources planning and management, and for engineering and design purposes. 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