Rio Grande Compact
Jan 21, 2022 Update - Without serious actions that reduce water depletions in the Middle Rio Grande, New Mexico will violate the Compact. The situtation is urgent. Middle Rio Grande total water depletions must be reined in. If not reined in, the US Supreme Court will decide Rio Grande water users' future.
New Mexico estimates its 2021 deliveries of water, for use below Elephant Butte Dam, were about -30,000 acre-feet short of meeting its 2021 delivery obligations. The 2021 annual debit brings the cumulative debit to -127,000 acre feet. The compact limits New Mexico's cumulative debit to -200,000 acre-feet.
Blogs, opinions, links, and announcements related to the Rio Grande Compact appear next, before a detailed summary of facts and issues.
Rio Grande Compact Background and Issues
Summary. The Rio Grande Compact is state law in New Mexico, Colorado, and Texas. It's federal law, also. It's a water sharing agreement signed in Santa Fe in 1938. It divides the waters of the Rio Grande upstream of Ft. Quitman, Texas. Each upstream state is required to deliver a variable portion of the water it receives to its downstream neighbor.
The US Supreme Count enforces the compact in disputes between states or with the United States. The committments of all parties are binding. They can be changed only by agreement of all the three states and the United States.
Upstream from Elephant Butte Dam, New Mexico has been in continuous compliance since 1969. Now, inadequate deliveries of water through the Middle Rio Grande for use in the Lower Rio Grande will cause a violation. At current trends, this new violation will occur in a year or two. New Mexico underdelivered approximately -30,000 acre-feet in 2021.
Total depletions in the Middle Rio Grande exceed the Middle Rio Grande's share.
Our Middle Rio Grande compact compliance problem is distinct from currrent US Supreme Court litigation. In the Lower Rio Grande downstream from Elephant Butte Dam, Texas and the United States are suing New Mexico over groundwater pumping in New Mexico that depletes Texas' and the US shares. New Mexico's counterclaims that Texas' unregulated groundwater pumping and downstream water management and deteriorated infrastructure share blame.
This issue description is written in six parts.
Middle Rio Grande Water Entitlements and Water Delivery Obligations
Middle Rio Grande Water Budget
Rio Grande Compact
The Rio Grande Compact requires over half the water flowing into the Middle Rio Grande annually at the Otowi gage to be delivered through the Middle Rio Grande for use by New Mexicans and Texans living downstream of Elephant Butte Dam.
Middle Rio Grande Allowable Depletions of Basin Inflows at the Otowi Gage Cannot exceed 405,000 Acre-Feet in Wet Years or 43% of Inflows in Dry Years. Source: NM Interstate Stream Commission
The compact caps the Middle Rio Grande's total depletion of Rio Grande flows due to all causes, human and natural. Human depletions include the net reduction in the river's flow caused by all diversions of water, including groundwater pumping from aquifers hydrologically connected to the river. Human depletions also include evaporation from water storage reservoirs. Natural depletions include water consumed by riparian areas adjacent to the river and evaporated from the river itself.
Middle Rio Grande Water Entitlements and Water Delivery Obligations
The required annual downstream delivery--to and through Elephant Butte Reservoir--is based on the annual flow entering the Middle Rio Grande as measured at the Otowi stream gage. The Middle Rio Grande is allowed to consume the difference between the annual water flow measured at the Otowi gage and the corresponding required annual downstream delivery. Tributary and arroyo inflows that reach the Rio Grande within the Middle Rio Grande are part of the Middle Rio Grande's annual share.
Annual stormwater runoff during the monsoon season is an important element of the Middle Rio Grande's legal water budget. Unlike inflows to the Middle Rio Grande at the Otowi gage, which establish the annual downstream delivery obligation and can be only partially used, tributary inflows to the river do not affect the delivery obligation while increasing the surface water supply and contributing to actual downstream deliveries.
Total annual consumptive water uses of surface water in the Middle Rio Grande that exceed the allowable difference between inflows at the Otowi gage and required downstream deliveries at Elephant Butte create an annual shortfall in downstream deliveries. This shortfall is called an annual compact debit. Conversely, if uses are less than the allowable amount, the result is an annual compact credit.
Cumulative debits less than -200,000 acre-feet per year are allowed but restrict storage of water in two Santa Fe River reservoirs and El Vado Reservoir on the Rio Chama. Cumulative debits greater than -200,000 acre-feet violate the compact.
Middle Rio Grande Water Budget
What is a water budget? It's conceptually the same as a financial budget. The Middle Rio Grande water budget compares the legally-available surface water supply (credits or income) with water depletions (debits or expenditures).
The Middle Rio Grande Water Supply Study was commissioned by the NM Interstate Stream Commission and the US Army Corps of Engineers in 1999 to develop an updated water budget for the Middle Rio Grande. The study, revised in 2004, compared the mean annual water supply that is legally available to be consumed within the Middle Rio Grande with the total depletion of water for year 2000 land use and groundwater development conditions.
The study results are illustrated below.
The 2004 Middle Rio Grande Water Supply Study Concluded Middle Rio Grande Average Depletions of Water are 40,000 Acre-Feet Per Year Greater than the Legally Available Water Supply
Green arrows illustrate the renewable components of the water supply that can be legally depleted in the Middle Rio Grande. Red arrows show total water depletions. The blue arrow shows the net supply, moving downstream from top to bottom.
The study concluded total depletions of the river's flows for year 2000 conditions exceeded the average annual legally available supply, 1950-2000, by 40,000 acre-feet per year. This is 6% of the study's quantification of total surface water depletions.
The bottom section of the graphic shows an average of 124,000 acre-feet of the Middle Rio Grande's legally available supply flowed annually into Elephant Butte Reservoir. However, reservoir evaporation losses averaged 164,000 acre-feet, creating an average excessive annual depletion of 40,000 acre-feet.
The yellow arrow indicates that groundwater pumping in 2000 was depleting the aquifer about 70,000 acre-feet per year. All depletions of the aquifer will, over time, deplete the river by the same amount. This study therefore indicated the gap between our water demand and our average available renewable supply was 110,000 acre-feet per year, which is 16%.
A group of academic and government experts working with the Middle Rio Grande Water Assembly prepared a detailed draft water budget in 2014. This budget relied on a very different technical approach but reached a similar conclusion.
Middle Rio Grande Water Depletions
The Middle Rio Grande Water Supply Study calculated the amounts of water depletions that would occur on average under year 2000 land use and groundwater development conditions. Human-caused and natural depletions were each about half of the total.
Average Depletions of Water in the Middle Rio Grande From the 2004 Water Supply Study. The Top Chart Shows Categories of Depletions. The Bottom Chart Adds a Geographic Breakdown.
History of Compact Compliance
Each year, the Rio Grande Compact Commission calculates whether the total annual quantity of water delivered through the Middle Rio Grande for use below Elephant Butte Dam was greater or less than required. The states have disagreed on the accounting since 2011.
The graphic below shows the cumulative credit or debit history since accounting began in 1940. The history behind the graphic would be a series of stories too detailed to summarize here.
New Mexico will violate the compact this year or next without bold actions to reduced Middle Rio Grande water depletions.
DANGER
In 2019, New Mexico's overuse of water in the Middle Rio Grande caused the first significant cumulative shortfall since 1990. Now, New Mexico's cumulative debit has grown to approximately -127,000 acre-feet.
Urgent action is required if New Mexico is to prevent the cumulative debit from exceeding the -200,000 acre-feet debit limit allowed by the compact.
Texas and the United States in 2012 sued New Mexico over Lower Rio Grande groundwater pumping. New Mexico has asserted counterclaims. A years long trial before a US Supreme Court special master is underway.
As long as deliveries of water through the Middle Rio Grande comply with the Rio Grande Compact, the Middle Rio Grande and its water users will not be impacted by the ongoing Lower Rio Grande US Supreme Court litigation.
If the Middle Rio Grande water delivery cumulative debit exceeds -200,000 acre-feet, the litigation will engulf all of the Rio Grande in New Mexico. Our water future will be in the hands of the US Supreme Court and it's Special Master.
In mid-2021, Texas filed a motion to expand the Lower Rio Grande litigation. The motion claims Middle and Upper Rio Grande violations. The premises of this motion are false. It is pending.
