Interesting lecture on the laws of water use in USA by Prof. Glennon given at the UC Berkeley California Colloquium on Water. Some of the facts cited in this talk:
- Groundwater use for domestic purposes alone 8 BGD (Billion Gallons per Day) in 1965 to 19.7 BGD in 2000.
- Farmers use 2/3 of all groundwater pumped.
- Total groundwater use in 2000: 30 trillion gallons
- Groundwater makes up 25% of the nation’s water supply
- 1/2 population relies on groundwater for drinking water
But these numbers are quite out of date. During the past decade people have turned to groundwater to supplement the short supply of water caused by draughts. This means that much more water must have been pumped from new and existing groundwater sources than in 2000 (the last year for which there is data from the US Geological survey).
Surface water law. If you own property on a lake or river, then you’ve water rights. This is called the Riparian Water Rights (which has its origin in English common law). It is a shared water rights (all land owners that are on the river or lake share the water rights). In the western USA, a different law is in place: Prior Appropriation. In this system, water rights are unconnected to land ownership. The first person to use a quantity of water for a beneficial use (agricultural, industrial or household use), has the right to use that quantity of water for that purpose. Each water right has a yearly quantity and an appropriation date.
Groundwater law: Rights of Capture & Reasonable Use. The problem with the groundwater law capture and reasonable use is that it allows for over-drafting or mining the resource to the extend of exhausting the supply. Basically anything you can with groundwater is considered reasonable.
San Joaquin Valley subsidence
These are the basic laws for water. One set of rules for surface water and one set for groundwater. Think of a ground water as a glass of water and each groundwater user having a straw. The groundwater laws allows for unlimited supply of straws. This leads to exploitation of groundwater aquifers.
Water is measured in acre-foot. That is how much water it takes to cover an acre of land to the depth of one foot with water. An acre water is 325,000 gallons, and weights 1358 tons. So water is really heavy and it takes a lot of energy to pump it out of the aquifers. Pumping water out of a 500 feet well will require many kilo watts of energy (multi $K per month).
Problems with over-drafting:
- The water quality is lower the deeper the well.
- Salt-water intrusion.
- Subsidence. The land collapse when groundwater is pumped too quickly without giving the aquifers times to naturally replenish (rate of 2 inches per year).
Groundwater moves laterally and it actually provides water to the rivers.
