By civil and environmental, do you mean civil/environemntal engineering? Cuz a statement like that would make a lot more sense coming from someone of that perspective.
I don't personally know about how much it would drain from the river directly off the top of my head, but i know for a fact that it threatens it's water and it's ecology. taking water form the river is not the only concern with building two dams, one being 4x the size of horsetooth (which is huge). dams trap water in a stagnant location and evaporate causing water displacement/loss, it builds up sediment that should otherwise be downstream and therefore causes downstream erosion, and it'll cost more than it is worth. This project not only endangers the Poudre river and it's ecology but it also would take away water from Agriculture in Northern CO.
Quoted directly from
http://www.savethepoudre.org/the-farm-facts.html
The Northern Integrated Supply Project (NISP) along with Glade and Galeton Reservoirs, threatens the agricultural economy of northern Colorado. Here's why:
NISP would accelerate the buy-up and subdivision of irrigated farms in northern Colorado;
NISP would accelerate salinization of productive crop lands;
NISP would end most "free river" diversion opportunities and impact many existing water users;
NISP would submerge and divide productive agricultural land;
The “Initial Fill” and ongoing diversions into Glade and Galeton Reservoirs are likely to come from northern Colorado and West Slope farm water.
NISP is not like the Colorado Big Thompson (C-BT) project. NISP would take water away from agriculture, not bring new water in for agriculture. NISP would help force the dry-up of 67,000 acres of irrigated farms in northern Colorado, and NISP could directly cause the temporary or long-term dry-up of an additional 56,000 acres of irrigated agriculture in northern Colorado and the West Slope.
If NISP is built, approximately 123,000 acres of agricultural land – 1/6th of all of the irrigated land in northern Colorado – could be negatively impacted.