Rio Grande Compact Commission annual accounting accruals 1940–2025 superimposed on Reclamation’s end-of-month full storage record 1915–2026. The physical, hydrologic accruals are much different.
The wettest two decades of the record, 1979 to 1998, built the credit that the dry decades since have spent.
The record floods of 1941–42, before Cochiti Dam, caused major sedimentation of the river channel, effectively destroying it, as shown by later aerial photographs of a salt cedar thicket without a discernible channel. Reclamation’s 1950s river channel straightening and channelization was part of the eventual response.
Elephant Butte Reservoir has filled and spilled in six years — 1942, 1985, 1986, 1987, 1988 and 1995. Under Article VI, a spill zeros the accounting balance and cancels that year’s accounting, which is why the line touches zero in those years and one reason why they are excluded from every statistical test.
The balance is annual and is not interpolated between years, because the accrual is a year-end quantity. The storage trace beneath it moves every month; the two are on different time steps.
What is plotted. Elephant Butte storage on the left axis; New Mexico’s cumulative Compact credit and debit balance on the right axis.
Basis. Storage is Reclamation’s daily record reduced to end-of-month values. The balance is the Commission’s accrued balance, annual, 1940–2025, expressed as an annual or cumulative credit or debit. In contrast, the hydrologic accruals are called over deliveries or underdeliveries.
Graphics features. Blue segments of the balance line are years that accrued a credit, red segments years that accrued a debit. The horizontal red line is the 200 KAF accrued debit limit set by Article VI and the band below it is the violation zone. Stars mark the spill years.
Interactive features. Hovering any year gives that year’s accrual with its sign, the running balance, the room left before violation, and the reservoir storage. In the nine years carrying a paper adjustment it also gives the size of the adjustment and what the river itself did. Year-window sliders narrow the record and a checkbox hides the annotations.
Data source. Reclamation Hydrodata, Elephant Butte daily storage 1915–2026 · Rio Grande Compact Commission accounting records, cumulative credits or debits, 1940–2025.