Case Study → Integrated Drainage Basin Management for Large Rivers - Colorado Drainage Basin

Context	● Colorado River is one of the major rivers of the USA ○ Has a basin size of 637, 000km^3 ● Its source is in the Rocky Mountains NW of Denver and it flows SW to the Pacific Ocean via Mexico ● Drains 7% of the USA and covers an area over 1x the size of France
Challenges of Managing it	● Large Basin & long river ● Large water demand & growing population ● Large part of the basin is desert or semi-arid ● 7 US states and Mexico take water from it ● Climate change is creating drier conditions and variable river levels

| Building
Pressures
| ● Mexico takes 10% of the total flow
● The states in the Lower Basin take 50% and the Upper basin falls short by 10%
● California takes 20% more than its allocation, which had been agreed separately in
1963
● Native Americans are owed 5% but they could claim more because their reservations
extend along the river and two of its tributaries |

| Agreements | ● Date back to 1922
○ Shared out water based on demand in 1956
● Since 1990 a new management agreements has been needed because
○ The states in the lower basin used all their share of water for the first time
○ Environmental regulations increased complexity
● In recent yrs there has not been enough water to supply demand, leading to
disputes and no agreement, especially between the US states |

upper Colorado River basin