Delta Lake (Nueces-Rio Grande River Basin)
Delta Lake (previously called Monte Alto Reservoir and has also been called Mesteñas Reservoir and Willacy Reservoir) is located four miles north of Monte Alto in Hidalgo County. It is an off-channel storage reservoir to the Rio Grande. The reservoir is owned and operated by the Hidalgo-Willacy Counties Water Control and Improvement District No. 1 for water supply, irrigation and recreation purposes. Authorization (Permit No. 1110) was issued by the State Board of Water engineers on January 9, 1930.
Construction to canal started 1936 and the reservoir was completed and impounded in 1939, According to communication with the owner, the lake has a capacity of 14,000 acre-feet and a surface area of 2,371 acres at the elevation of 56.5 feet above mean sea level and consists of two units. Water is diverted from the Rio Grande in Cameron County by a gravity canal system. From this main canal water is diverted to another canal, known as Mesteñas Canal, for distribution to land during the irrigation season or to a pumping plant that lifts surplus water to the reservoir for storage. When needed for irrigation, the water is released and flows back to the Mesteñas Canal for distribution.