5
votes
Accepted
How much air gap is required in a storm pipe?
You're right, if your pipe is completely full then you don't have open channel flow. In other words, you can no longer use Manning's equation to model the flow in that pipe. You would have to use ...
- 426
3
votes
Trinity Lake Leak
"Reclamation began the project last fall to rehabilitate the
reservoir’s hemispherical bulkhead during low lake levels.
Reinstallation of the bulkhead began on March 6 and requires a
temporary ...
- 31
3
votes
How to cut a pipe such that water comes out evenly across the length?
There is a better way sometimes used for ponds. It avoids the large maintenance job you will have cleaning the inlet to your pump.
Dig out an area for pond and wetland. Lay a good size (like 4") ...
- 6,102
3
votes
How much air gap is required in a storm pipe?
There are additional features of the air gap besides pressure relief (Especially in small domestic pipes).
Maintenance clean out access
View port for viewing if flow is blocked
Alleviating a small ...
- 5,343
3
votes
Why do dams deplete rivers?
The answer has nothing to do with Bernoulli's equation.
A large dam across a steep canyon will define a large catchment volume. It is not uncommon for such a catchment to take as long as ten years to ...
- 14.1k
2
votes
Why do dams deplete rivers?
Some dams are designed to even out the natural river flow so that the level or height of the river is relatively constant.
The natural change in rainfall over time causes a natural change in river ...
- 15.3k
2
votes
Why is the wet/dry boundary of ground not dangerous for foundations?
That water you have described where the ground is wet but the lower ground at the foundation levels were dry, is generally not going to cause significant problems because the weight of the water will ...
- 298
2
votes
Why is the wet/dry boundary of ground not dangerous for foundations?
Depending on the type of soil at your site, moisture content under the foundation can change depending on the change in surrounding soil.
The typical footing depth in the majority of cases will be ...
- 21.8k
2
votes
Terminology for ponding behind a bridge during a flood
I believe that the phrase that you are looking for is either backwater or headwater.
Image from from http://epg.modot.org/index.php?title=748.4_Headwater_and_Backwater
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2
votes
Why do dams deplete rivers?
I suggest that this is not an engineering problem, but a political one. Yes, dams reduce flow downstream when they are filling up, but this isn't a long-term issue. The issue is that once a dam is ...
- 6,276
2
votes
Accepted
Why were so Many Older Bridges Built so Low to the Water?
Cost
It costs more to build a 23 mile bridge 20 feet (30 feet, 40 feet?) higher in the air.
When it was built, the Lake Ponchartrain Causeway wasn't blocking anything - there was zero freight traffic ...
- 6,276
2
votes
Accepted
How much energy is needed for the USA to only use desalinated water?
Amount of Water Used
The amount of water used in the USA in 2015 for all uses other than thermoelectric power (1) (read: to cool power plants) was 189B gal/day, or 715M m^3/day.
Amount of Energy ...
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1
vote
Accepted
Trinity Lake Leak
As Walt's answer points out, water is being dumped for "flow augmentation". I.e., environmental purposes. The specific program is the Trinity River Restoration Program which aims “to restore ...
- 111
1
vote
Can saline water be used in a hydro storage system and would the ambient temperature or higher liquid viscosity affect performance?
NOT a hydroelectric engineer, but I have spent a lot of years developing fluid systems using saline and related liquids.
To answer the basic question: yes saline works for hydro storage systems.
But ...
- 99
1
vote
Determining depth of flow in open channel flow
To solve for depth, given flow, one can use VT Chow’s equations to iteratively solve for theta. The two solutions will be found on either side of theta Qmax.
Chow on internet
- 154
1
vote
Accepted
Is VLF-EM scanning for fractures a valid way to find groundwater for a well?
The answer above is wrong. VLF-EM equipment isn't using the VLF signal as 'radar' and looking for scattering. THE VLF signal induces an electromagnetic response in conductive rocks, and the measuring ...
1
vote
Is VLF-EM scanning for fractures a valid way to find groundwater for a well?
Nope. Here is why:
VLF frequencies have wavelengths between a thousand meters and ten thousand meters. To scatter off a feature with a scale length of order ~1000 meters (like a subsurface fracture) ...
- 14.1k
1
vote
Differences between 2D hydrological modelling programs eg. HECRAS 5.0 (2D), TUFLOW, MIKE Flood
The critical thing to be aware of is the suitability of application, and stability for that application. Noting that generally Finite Volume methods result in better accounting for volume hence mass ...
- 11
1
vote
Determining RTK parameters for runoff analysis
If your watershed is in the U.S., you might find TR-55 useful. "Technical Release 55 (TR-55) presents simplified procedures to calculate storm runoff volume, peak rate of discharge, hydrographs, and ...
1
vote
Open Channel flow with pressure losses - flow depth?
If the channel is horizontal, the flow will set a slope to use the head lost as a potential energy to turn it to kinetic energy that is required to overcome the head loss at the bends and also the ...
- 21.8k
1
vote
What is the technical name for a water reservoir that retains its contents via vacuum and ambient air pressure?
A Torricelli vacuum, and barometers with mercury apply the same principle.
- 15.3k
1
vote
What is this structure in a park
As Jem Eripol points out, it is to prevent erosion / collapse of the earth above it. Likely the land was cleared and leveled to produce the park, and to prevent the hillside above it from filling in ...
- 126
1
vote
Peak flow calculation using rainfall data
According to TR-55, here, you use total rainfall. This requires a bit more information about the watershed, namely the time of concentration (which affects the unit peak discharge). Then, from TR-55:
...
- 21
1
vote
What is the difference (if any) in capacity factors and efficiency between reservoir hydropower and run-of-river power plants?
Capacity factors over a plant's lifetime are largely a design decision. There is no standard one-size-fits-all answer. The situation in any one particular case will be determined by the local climate ...
- 3,741
1
vote
Transporting water uphill at the highest efficiency possible?
Hydroelectric dams approximate your description.
Look at the below schematic diagram of a hydroelectric power plant. As you can see, the kinetic energy of the water flow spins a turbine which powers ...
- 519
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