This is the process of how the groundwater becomes part of larger bodies of water.
http://pubs.usgs.gov/fs/fs15099/
The headwaters of the Colorado River is located in Rocky Mountain National Park in Colorado on the west side of the Continental Divide. The elevation is high at over 10,000 feet and the headwaters is subject to unpredictable weather patterns that consist of heavy snows, rains, lightening storms, as well as hot weather in the summer (Triedman). Up until 1921, the entire section of the Colorado River that is above its confluence with the Green River in Eastern Utah was called the Grand River. This is why Grand Lake, Grand Valley, and Grand Junction are named such. This area is the headwaters of the Colorado River and just below it, however, now it is just called the Colorado River (Barkley) (Triedman). Although it is accepted that the headwaters reside in Rocky Mountain National Park, there is a debate over the direct source of the headwaters. While many argue that the direct headwaters are La Poudre Pass Lake, a new study was just released that points to snow melt and groundwater as the sustaining water sources (Tory).
Even the scientists who believe that La Poudre Pass Lake is the headwaters acknowledge the role that snow melt plays in sustaining the Colorado River. As spring comes and the snow melts, it is captured by streams and rivulets that flow down the Rocky Mountains that eventually feed into the mighty Colorado River (Colorado River). However, in the study released by the United States Geological Survey, the significant role that groundwater plays in the Colorado River watershed is revealed. It was always known that groundwater was a major source of water as the river needed to be sustained once the rapid snow melt subsided in the summer and fall months. However, the study revealed that 50% of the water from the upper Colorado is sustained by groundwater (Tory). This groundwater is in the form of small rivulets beneath the ground that are thousands of years old which find their way to the Colorado by surfacing and flowing into the streams and rivulets which feed the Colorado or through percolating down through the ground and becoming part of underground aquifers that provide water to the river.
This conclusion was determined by measuring the electrical conductivity in the water of the Colorado River. The conductivity of water is very revealing of its journey. Water with low conductivity exposes that the water has not had the time to pick up ions from flowing over or through the ground, while water with high conductivity has had the time to flow through soil and rocks and gain ions. When the water conductivity of the Colorado was measured, the data regarding the water ion levels was compiled and used to determine the percentage of water that was from snow pack and the percentage that was from groundwater. The team of scientists, led by head Matthew Miller, revealed that 56% of the water was of a high conductivity grading. This means that 56% of the water in the Colorado River Basin stream flow is from groundwater because groundwater has had trickled through soil and rocks for thousands of years and has thus gained ions. In contrast, water from snow pack has just melted and has not had the exposure or time to gain ions (Tory).
In terms of environmental conditions for the headwaters, the source is relatively pristine as both La Poudre Pass Lake and the rivulets of groundwater and snow melt are relatively isolated due to their elevation of 10,000 feet and the rugged terrain surrounding them (Triedman). The water in the headwaters is of especially high quality in comparison to water in the rest of the country. However, the rising levels of nitrogen depositions found in the surrounding soil through which the water percolates and flows into the lake and streams of the headwaters is a rising concern to those monitoring the river source. The nitrogen is thought to be worsened by the decreased levels of soil and rock surrounding the lakes and streams as both become more eroded. If nitrogen levels continue to rise in La Poudre Pass Lake, the environmental damage could be compounded by the fact that since the mountain air is so cold, very little evaporation occurs. This keeps the nitrogen stored in the water, and allows it to continue building up as the headwaters continues to be exposed to them. High levels of nitrogen deposition can result in acidification of water bodies that have the potential to permanently damage surrounding organisms (Water Quality).
La Poudre Pass Lake
La Poudre Pass Lake sits high in the Rocky Mountains at 10,000 feet elevation. Many scientists believe that it is the source of the mighty Colorado River.
http://www.protrails.com/gallery/536/colorado/rocky-mountain-national-park/Milner%20Pass%20Trail