At first glance, this might look like just another quiet desert reservoir.
But this is a place where water has nowhere to go.
Mursha Reservoir sits within a closed drainage basin, meaning water that collects here does not flow to a river, lake, or ocean. Even though the Colorado River is only a few miles to the east, the water here will never reach it.
Why? Because you are standing in a natural bowl.
A Landscape Built to Trap Water
This valley is part of the Basin and Range Province, a region formed as Earth’s crust stretched and broke apart over millions of years. Large blocks of land dropped down to form valleys, while others rose to create mountain ranges.
The result is a repeating pattern of basins and ranges — and Eldorado Valley is one of those basins.
Surrounded by higher terrain like the McCullough Range and the Eldorado Mountains, this valley has no outlet. Water flows downhill into it… and stops.
What Happens to the Water?
When rain falls in the valley, water flows toward the lowest areas, sometimes forming temporary lakes across the basin floor.
But without an outlet:
- Water cannot drain away
- It collects briefly
- Then it disappears
Most of it evaporates, while some soaks into the ground.
As the water disappears, it leaves behind fine sediments and dissolved minerals, forming flat, often cracked surfaces known as playas, or dry lake beds.
Those polygon-shaped cracks form as wet mud dries, shrinks, and splits under the intense desert heat.
Shaping the Valley
Look toward the mountains and you may notice wide, fan-shaped slopes spreading out into the valley.
These are alluvial fans, formed when flash floods carry sediment out of the mountains and deposit it as the land flattens. Over time, these deposits help build the valley floor while maintaining the basin’s shape.
Why This Matters
This landscape tells a much bigger story than just a reservoir:
- How Earth’s crust stretches and forms basins and mountains
- How water behaves in a closed system
- How deserts record cycles of flooding and evaporation
Mursha Reservoir exists because of all of these processes — and because in this valley…
👉 water has nowhere else to go.
Logging Requirements
To log this EarthCache, visit the site and answer the following questions. Send your answers via message. Do not include answers in your public log.
1. Basin Clues
Based on what you can observe, what evidence suggests that this valley is a closed (endorheic) basin rather than one that drains to a river?
2. Water’s Fate
After rainfall, what are the two main ways water leaves this basin?
3. Surface Features
Look at the ground around you. Do you see any signs of a playa (dry lake bed) such as flat surfaces, fine sediment, or cracking? Describe what you observe.
4. Mountain Connection
Observe the slopes where the mountains meet the valley. Do you see any fan-shaped deposits (alluvial fans)? What do they tell you about how sediment moves in this environment?
5. Photo (Required)
Take a photo of yourself, your GPS, or a personal item at the site (no spoilers).
Desert Safety
The Mojave Desert is beautiful, but it can also be unforgiving. Please come prepared:
- Bring plenty of water — more than you think you’ll need, especially in warmer months
- Avoid peak heat in summer; temperatures can exceed 110°F
- Wear sun protection (hat, sunscreen, sunglasses)
- Watch your footing — loose gravel and uneven terrain are common
- Be aware of wildlife, including snakes and insects.
Sources & Further Reading
The geology described in this earthcache is drawn from published scientific sources. Cache visitors interested in going deeper are encouraged to explore the following:
1. Nevada Bureau of Mines and Geology (NBMG), 2017.
Preliminary Geologic Map of the Boulder City 7.5-Minute Quadrangle, Clark County, Nevada.
NBMG Open-File Report OF2017-05.
Available at: pubs.nbmg.unr.edu
(Primary source for alluvial fan descriptions, fault mapping, rock unit ages, and the drainage divide between Eldorado Valley and the Colorado River Basin.)
2. Northern Arizona University Southwest Virtual Museum.
Basin and Range.
Available at: swvirtualmuseum.nau.edu
3. U.S. Geological Survey (USGS).
Boulder City SW 7.5-Minute Topographic Quadrangle.
Available free at: topozone.com.