Thousands of Northern New Mexico gardeners and farmers who depend on the small Santa Cruz Lake for irrigation water were already having a tough year due to drought. Now they face the high likelihood of major damage to the lake, dam and irrigation works from debris, ash and floods expected from a nearby wildfire burn scar.
The Jaroso Fire has burned more than 11,000 acres in the Pecos Wilderness. Rain on the west side of the burn scar is expected to wash logs and debris into Santa Cruz Lake and could flood small downstream villages, such as Cundiyó and Rio Chiquito, north of Santa Fe. Storm runoff from the burn scar could also affect the upper Pecos Canyon.
Jim Snyder, a hydrologist with the specialized Forest Service team that assesses post-wildfire damage, said the amount of rain it would take to cause major flood damage depends on a lot of variables, such as the soil moisture and where the rain falls. By one estimate, 2.8 inches of rain falling on the west side of the burn scar over a six-hour period would cause major flooding and damage to the Santa Cruz Lake. “With two to three days of steady rain before that, the soils would be more saturated, and it would take less rain to cause flooding,” Snyder said.
The Santa Cruz Lake, a popular fishing spot for anglers, is fed by the Rio del Medio and Rio Frijoles. Portions of the upper watersheds of both rivers were burned in the lightning-started Jaroso Fire. The lake is privately managed by the Santa Cruz Irrigation District, which serves more than 4,000 irrigators and waters 3,000 acres of orchards, alfalfa fields, gardens and commercial farms around the Española Valley.
Rain fell in the area Saturday, and the irrigation water from the Santa Cruz Lake was a little murky with ash and silt on Sunday, said Charlie Esquibel, irrigation district manager. “But there has not been a lot of debris. It hasn’t rained heavily, thank God.”
Esquibel said irrigators were already feeling the water squeeze from the third year of drought and ongoing problems with silt in the lake. Now there’s the specter of burned logs, ash and debris clogging up the dam and shutting down irrigation. Nambé Lake had a similar problem in 2011 after rain pelted the Pacheco Fire scar, sending thousands of logs into the reservoir.
Until last year, Esquibel said, snowmelt filled up the Santa Cruz reservoir and spilled over the dam, providing plenty of irrigation water until at least mid-June. Then enough water is released from the lake to irrigate four days a week.
This year, there wasn’t much snowpack in the Sangre de Cristo Mountains, and the lake levels were already so low that the water didn’t spill over the dam. Esquibel has only released water two days a week for irrigators, about 12 hours a day. “Some of these irrigators have 500 acres, and there’s no way you are going to irrigate that much land with water only two days a week,” he said.
He said the district had planned to raise money to raise the dam height by 8 feet. Those plans may have to be set aside until the risks of flooding are over.
Camping, boating and fishing on the lake also will be affected by floods. The federal Bureau of Land Managment manages the recreation on the small lake. For the moment, recreation on the lake remains open.
Snyder said the large wildfires seen more frequently each year actually help create the right weather conditions for the very thunderstorms that then cause flooding. He said 25-year flood events (meaning the largest amount of water flows seen in that time period) happened after each of the recent large wildfires. Floods following the 2011 Las Conchas Fire wiped out the Dixon Apple Farm and damaged Santa Clara Pueblo lands. Floods off the Little Bear Fire scar ruined Bonito Lake, Alamogordo’s drinking water supply.
“You tend to see larger thunderstorms over fire scars,” Snyder said, especially when the fire has burned areas so hot there is no vegetation or even seeds left in the soil. He said more than half of the acreage burned in the Jaroso Fire was severely burned. Black, bare soils absorb sunlight and increase convection as the lower air heats up and moves through cooler air. Convection is one of the primary ingredients in the formation of thunderstorms.
Contact Staci Matlock at 505-986-3055 or firstname.lastname@example.org. Follow her on Twitter @StaciMatlock.