KGA Irrigation Toolsដំណើរការជាបាច់
Reservoir Rating Curve
គណនាលំហូរចេញសរុបពីអាងស្តុកទឹក នៅគ្រប់កម្រិតទឹក រួចគូសខ្សែកោង stage–discharge។ មួយ CSV និងមួយ PNG ក្នុងមួយ DEM។
- រកឃើញនៅឯណា
- Processing ▸ Toolbox ▸ KGA Toolbox ▸ KGA Irrigation Tools ▸ Reservoir Rating Curve
- លេខសម្គាល់ algorithm
- kga:reservoir_rating_curve
- ប្រភេទឧបករណ៍
- Batch algorithm
ទិដ្ឋភាពទូទៅ
The DEM only sets the elevation range, and the boundary clips it. Discharge itself comes entirely from the outlet definitions — no storage routing is involved, so the curve is static. Pair it with Storage Capacity Curve for the volume side.
Formulas
- Weir:
Q = C × L × H^1.5 - Orifice and pipe:
Q = Cd × A × √(2gH), with g = 9.81 m/s²
H = water level − activation elevation. An outlet contributes nothing while H ≤ 0, which is what puts the kinks in the total curve.
Typical coefficients
| Outlet | Coefficient |
|---|---|
| Sharp-crested weir | C = 1.84 |
| Broad-crested weir | C = 1.70 |
| Ogee spillway | C = 2.0–2.2 |
| Sharp-edged orifice or pipe | Cd = 0.61 |
| Rounded entry | Cd = 0.80–0.90 |
ប៉ារ៉ាម៉ែត្រ
| ឈ្មោះ | ប្រភេទ | តម្លៃលំនាំដើម | ការពិពណ៌នា |
|---|---|---|---|
| DEM Raster Layer(s) | Multiple raster layers | — | One curve per DEM. |
| Reservoir Boundary (optional — leave blank for full DEM) | Vector layer, optional | empty | |
| Elevation Step (m) | Number (min 0.001) | 0.1 | |
| Outlet Definition Mode | Enum | Fixed slots — up to 3 outlets, defined below | Or CSV file — any number of outlets, from a table. In CSV mode the three slots below are ignored. |
| CSV Mode · Outlet Table (.csv) | File (*.csv), optional | empty | Columns: outlet_id, type, act_elev, LA, C_Cd. |
| Output Folder | Folder destination | — |
Outlet slots 1, 2 and 3
Each slot repeats the same five controls. Slot 1 is enabled by default as a weir; slots 2 and 3 are off, pre-filled as an orifice and a pipe.
| ឈ្មោះ | ប្រភេទ | តម្លៃលំនាំដើម | ការពិពណ៌នា |
|---|---|---|---|
| Outlet N · Enable | Boolean | True / False / False | |
| Outlet N · Type | Enum | Weir / Orifice / Pipe | |
| Outlet N · Activation Elevation (m) | Number | 0.0 | The crest or centreline level. |
| Outlet N · Size — L (m) or A (m²) | Number (min 0.001) | 1.0 / 0.5 / 0.3 | Crest width L in metres for a weir, or opening area A in m² for an orifice or pipe. Areas are not derived for you — enter the computed value. |
| Outlet N · Coefficient — C or Cd | Number (min 0.001) | 1.84 / 0.61 / 0.61 |
Advanced
| ឈ្មោះ | ប្រភេទ | តម្លៃលំនាំដើម | ការពិពណ៌នា |
|---|---|---|---|
| Plot · Elevation Axis Minimum / Maximum (m) | Number | 0.0 (auto) | |
| Plot · Discharge Axis Maximum (m³/s) | Number | 0.0 (auto) | |
| Plot · Elevation Tick Interval (m) | Number | 0.0 (auto) | |
| Plot · Discharge Tick Interval (m³/s) | Number | 0.0 (auto) | |
| Plot · Resolution (DPI) | Integer (72–600) | 150 |
CSV table format
| outlet_id | type | act_elev | LA | C_Cd |
|---|---|---|---|---|
| 1 | Weir | 40.0 | 5.00 | 1.84 |
| 2 | Orifice | 35.0 | 0.20 | 0.61 |
| 3 | Pipe | 33.5 | 0.07 | 0.61 |
outlet_id must be unique — it names the output column. type must be exactly Weir, Orifice or Pipe.
របៀបប្រើ
- Load the DEM and the reservoir boundary.
- Open KGA Irrigation Tools > Reservoir Rating Curve.
- Define the outlets. For up to three, fill in the slots on the form; for more, switch Outlet Definition Mode to CSV and supply a table.
- Check that the activation elevations are in the same vertical datum as the DEM. This is the mistake that produces a flat zero curve.
- Press Run.
- To compare several reservoirs on identical axes, pin the axis ranges and tick intervals under Advanced and run again.
លទ្ធផល
Per DEM, in the output folder:
rating_{DEM}_{boundary}.csv— elevation, one column per outlet, andQ_total.rating_{DEM}_{boundary}.png— the curve, with each outlet's contribution shaded, its activation level marked, andQ_totalcrossed at every grid line for reading off.
កំណត់សម្គាល់ និងដែនកំណត់
- Activation elevations must be in the same vertical datum as the DEM. If they all sit above the DEM's highest cell the curve comes out flat at zero, and the log warns about it.
- Areas are not derived for you. For an orifice or pipe,
LAis the opening area in m² — compute it from the diameter yourself. - No storage routing. This is a static stage–discharge relationship, not a flood-routing result. It does not tell you how long the reservoir takes to draw down.
- The curve's kinks are real: they are where each outlet activates.