Hydraulic Potential Shreve
Evaluate Shreve hydraulic potential p_w+rho_w·g·bed elevation with caller water/overburden ratio; potentials share a vertical datum and no geodesy transform is performed.
Description
Subglacial hydraulic potential combines water pressure with gravitational potential at the bed.
Subglacial hydraulic potential combines water pressure with gravitational potential at the bed. Bed elevation and ice overburden jointly influence water routing.1
Evaluate Shreve hydraulic potential p_w+rho_w·g·bed elevation with caller water/overburden ratio; potentials share a vertical datum and no geodesy transform is performed.
When to use Hydraulic Potential Shreve
Use this for the following task: Evaluate Shreve hydraulic potential p_w+rho_w·g·bed elevation with caller water/overburden ratio; potentials share a vertical datum and no geodesy transform is performed.
Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
How to use Hydraulic Potential Shreve and understand its results
- Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
- Enter bedElevationsM, iceThicknessesM, waterPressureOverburdenFraction, iceDensityKgPerM3, waterDensityKgPerM3, gravityMPerSecondSquared using the field table, then run the tool.
- Read hydraulicPotentialsPa. Interpret flags, units, ordering and placeholder values using the rules below.
- Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| bedElevationsM | Bed elevations m | list of number; each entry: number | Required |
| iceThicknessesM | Ice thicknesses m | list of number; each entry: number | Required |
| waterPressureOverburdenFraction | Water pressure overburden fraction | number | Required |
| iceDensityKgPerM3 | Ice density kg per m3 | number | Required |
| waterDensityKgPerM3 | Water density kg per m3 | number | Required |
| gravityMPerSecondSquared | Gravity m per second squared | number | Required |
Pair bed elevations and nonnegative ice thicknesses. Apply a caller-supplied nonnegative water/overburden ratio and return potentials in pascals.2
Φ = ρwater g bedElevation + pressureRatio ρice g H This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| hydraulicPotentialsPa | Hydraulic potentials pa | list of number |
{
"input": {
"bedElevationsM": [
0,
100
],
"iceThicknessesM": [
100,
200
],
"waterPressureOverburdenFraction": 0.5,
"iceDensityKgPerM3": 900,
"waterDensityKgPerM3": 1000,
"gravityMPerSecondSquared": 10
},
"output": {
"hydraulicPotentialsPa": [
450000,
1900000
]
}
}Limitations and assumptions
Elevations must share a datum. Ratios above one are accepted, and no geodesy transform or drainage routing is performed.
Constants and empirical coefficients are supplied rather than calibrated. Check units and observational applicability before interpreting the model. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.
Alternative or Complementary methods
Choose Subglacial Flow Direction Gradient for this operation: Compute isotropic downhill hydraulic-potential direction from bed/thickness gradients and pressure ratio; flat gradients have no defined direction and anisotropic transmissivity is excluded. For a complementary task, use Effective Pressure Nye for this operation: Calculate signed ice-overburden minus subglacial water pressure and flag pressure above overburden; negative effective pressure is not clamped or interpreted as stable contact.
Further background: Subglacial hydrology.
References
-
Subglacial hydrology — PISM
-
Hydraulic Potential Shreve — tool.io
Similar or alternative tools
- Subglacial Flow Direction Gradient
Compute isotropic downhill hydraulic-potential direction from bed/thickness gradients and pressure ratio; flat gradients have no defined direction and anisotropic transmissivity is excluded.
- Effective Pressure Nye
Calculate signed ice-overburden minus subglacial water pressure and flag pressure above overburden; negative effective pressure is not clamped or interpreted as stable contact.