Here’s an in-depth look at the sedimentation problem at Paonia Reservoir from Emily Benson writing for The High Country News. Here’s an excerpt:
The root cause of the problem at the reservoir had been building since the dam was finished in 1962. Year by year, sediment quietly collected on the reservoir bottom, gradually raising its floor. Once the sediment was level with the dam outlet, where water is released downstream, any debris that washed into the reservoir threatened to clog the opening and make the dam inoperable. In the fall of 2014, personnel worked 10-hour days for two weeks to clear logs, branches and dirt from the outlet, by hand and with an excavator. Some of the workers stood directly on waterlogged sand, digging out the grates with pitchforks. When the dam was newly built, they would’ve needed a crane 70 feet tall to reach the same spot.
Silt, sand, gravel and clay are accumulating in nearly all reservoirs in the West, leaving less room to capture water for storage or for flood prevention. Behind many dams, space is starting to run out. Ignoring the problem could jeopardize the West’s water supply in the coming years. To avoid that, water managers are dredging behind dams, retrofitting outlet works and looking for ways to safely pass sediment downstream. “It’s not an immediate crisis,” Randle says. “But it is sort of a ticking time bomb.”
Click through and read the whole article from the Valley Morning Star (Norman Rozeff). Here’s an excerpt:
Importantly the United States and Mexico needed an agreement on the appropriation of waters in the lower Rio Grande. This was wrought in a mutually ratified treaty that stated that Texas would have all the rights from its own tributaries and that Mexico would assure 350,000 acre-feet annually to Texas from Mexican tributaries.
The treaties also anticipated the construction of two major reservoirs on the river.
These were to be Falcon Dam, completed in October 1953, and Amistad Dam, completed in 1969. Also established by the treaty was the International Boundary and Water Commission charged with coordinating the work between the two countries.
The ability of the flood control system to operate successfully was put to the test on September 20, 1967 and the days to follow as Category 3 Hurricane Beulah made landfall just north of the mouth of the river.
It was a slow moving system that dumped massive amounts of rain over the Valley and points west in the river’s watershed over a three day period. Heavy storms in August has previously saturated much of the LRGV.
At Rio Grande City the peak discharge occurred on September 22 at 210,00 cubic feet per second and 10 feet above flood stage. On the 25th, Mission experienced 206,000 and also 10 feet while on the 26th Hidalgo had 81,000 cfs and 6 feet. On the 29th San Benito registered 25,00 cfs and 6 feet above flood stage. The following day Brownsville registered 16,000 and 1 foot respectively.
The floodway was soon inundated with overflow waters from the rivers as well as runoff from the cities.
The airport of the City of McAllen was flooded on September 26 by waters from the Mission floodway that overpoured high ground about three miles west of the airport.
As floodway waters reached the division point near Progreso the majority of the flow diverted into the Arroyo Colorado.
This soon resulted in urban areas along the Arroyo in Harlingen being submerged by the flooded stream.
The crest was ten feet higher than that occurring in 1958 when in October-November spills at Falcon Dam and flood inflows from the San Juan River were the culprits.
An estimated 8,000 people, about 20 percent of the city’s population, required evacuation…
While it didn’t pass the House, it may have laid the groundwork for later appropriations, for in February 1971 Congress appropriated $29 million for the first phase of Valley flood control.
From Cronkite News (Kianna Gardner) via the Arizona Daily Sun:
The adult quagga mussel finding [on March 3, 2013], coming less than a year after [veligers] were first spotted, marked the end of more than a decade of attempts to keep the invasive species from taking over Lake Powell and cued the beginning of a new fight.
Experts deem it impossible to entirely eradicate the mussels from Lake Powell, a tourist destination that spans Utah and Arizona. The mussels latch on to the walls of Glen Canyon Dam and the hundreds of boats skimming the lake’s waters. If the mussels could not be removed from the lake, the experts concluded, at least they might contain the threat to keep it from spreading to other waters.
Clumps of quagga mussels damage the dam’s water flow, undercut an ecosystem for other aquatic species, cling to boat engines and cost millions of dollars to handle.
“It was a huge responsibility and honor to try and protect this lake. It is still a huge responsibility and honor to contain the quagga mussels here,” said Colleen Allen. She holds a distinctive title as a leader in the quagga mussel incursion: aquatic invasive species coordinator for Glen Canyon National Recreation Area.
The quagga mussel, a freshwater mollusk that likely was unwittingly brought into Lake Powell by boat, have proven to be a small but mighty foe. Less than three years after finding that mussel, the invasion had spread throughout most of the 186 miles of Lake Powell. Today, quagga mussels can be found in every canyon crevice, Glen Canyon officials said.