DELTA LAKE. Delta Lake, in the Nueces-Rio Grande basin four
miles north of Monte Alto and twenty-four miles northeast of
McAllen in Hidalgo County (at 26°25' N, 97°56' W), was
previously called Monte Alto Reservoir and has also been called
Mesteñas Reservoir and Willacy Reservoir. It is an off-channel
storage reservoir to the Rio Grande. The project, constructed in
1939, is owned and operated by the Hidalgo-Willacy Counties
Water Control and Improvement District No. 1. It has a capacity
of 25,000 acre-feet and a surface area of 2,371 acres at the
elevation of 56½ 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.