The Spring watershed (HUC 03130010) is located in north-central Colorado and covers an area of approximately 1,671 square miles. The hydrology of the watershed is heavily influenced by the Rocky Mountains and experiences a snowmelt-dominated hydrologic regime. The watershed is characterized by a specific snowpack that accumulates throughout the winter months and typically begins to melt in March or April. This snowmelt contributes to the surface water in the watershed, which is primarily composed of streams and rivers. The major reservoir in the watershed is Horsetooth Reservoir, which is used for water supply, recreation, and flood control. Interesting climatic facts for the area include the occasional occurrence of severe droughts and intense precipitation events, both of which have increased in frequency and intensity in recent years. There is also a trend toward earlier snowmelt and decreased snowpack in the watershed, which could have significant impacts on water resources in the future.