Niangziguan Spring, a karst fissure spring, is situated in the vicinity of the Niangziguan, Shanxi Province. Its average annual flow is 12.6m3/s, and it has a drainage area of 3,560km2. It is one of the largest springs in China. The mathematical model of this spring may be written as: Where Q is the discharge of the spring ( m3/s ) ; P, precipitation ( mm ) ; W, coefficient of weight; a, error of discharge ( m3/s ) ; and t, time ( year ) . Using the observation data of discharge and ...