(NASA) – Elephant Butte Reservoir dwindled to its lowest level in 41 years during the summer of 2013, despite monsoon rains in early July. It had been filled nearly to capacity for most of 1985 to 2000; the left-hand image from 1994 shows it about 89 percent full. At right, it has been reduced to about 3 percent. Elephant Butte is fed by the Rio Grande and is New Mexico's largest reservoir. It provides water for about 90,000 acres (364 square kilometers) of farmland and nearly half the population of El Paso, Texas. Spring runoff from mountain snowpack was well below average in spring, 2013, and anemic rains throughout the beginning of the year left 80 percent of New Mexico grappling with either "extreme" or "exceptional" drought, the two most severe categories.