Susceptibility level | Erosion rate [t · ha-1 · a-1] | Area [km2] | Percentage [%] |
---|---|---|---|
Very low | <15 | 16.098 | 39.62 |
Low | 15–60 | 3.820 | 9.40 |
Moderate | 60–180 | 5.002 | 12.31 |
Severe | 180–480 | 6.157 | 15.15 |
Very severe | >480 | 9.559 | 23.52 |
Total | 40.635 | 100.00 |
Month | Monthly discharge [mln m3 · month-1] | |||||
---|---|---|---|---|---|---|
2017 | 2018 | 2019 | 2020 | 2021 | Average | |
January | 16.550 | 14.309 | 17.586 | 13.622 | 17.695 | 15.952 |
February | 11.238 | 15.589 | 9.324 | 12.242 | 15.549 | 12.788 |
March | 4.765 | 14.807 | 10.392 | 20.843 | 9.117 | 11.985 |
April | 11.047 | 8.404 | 2.685 | 6.525 | 7.566 | 7.245 |
May | 1.168 | 0.716 | 1.713 | 8.857 | 9.502 | 4.391 |
June | 0.884 | 2.237 | 0.094 | 2.039 | 3.228 | 1.696 |
July | 0.009 | 0.922 | 0.033 | 0.386 | 5.191 | 1.308 |
August | 0.292 | 0.010 | 0.596 | 0.581 | 0.317 | 0.359 |
September | 2.000 | 0.009 | – | 0.973 | 1.482 | 1.116 |
October | 4.415 | 0.003 | 0.033 | 24.668 | 4.568 | 6.737 |
November | 10.140 | 11.840 | 1.071 | 26.127 | 10.569 | 11.949 |
December | 13.430 | 0.229 | 3.768 | 18.865 | 15.547 | 10.368 |
Annually discharge [mln m3·a-1) | 85.897 |
Data | Data source |
---|---|
Depth of reservoir (2023) | Field survey |
Sediment’s specific gravity (2023) | Field survey |
Digital elevation model | Indonesia Geospatial Information Agency |
Land-use data (2020) | Indonesia Geospatial Information Agency |
Rainfall data at Sempor, Sampang, Somagede and Kedungwringin Stations (2009–2020) | Water Resources Management Center for Progo-Bogowonto-Luk Ulo; Main Station of Serayu-Opak River Basin |
Parameter | Equation |
---|---|
Trap efficiency TE [%] | |
Sediment yield G [t·a-1] | G = SDR × Ea |
Reservoir capacity [m3] | Annually discharge [mln m3 · a-1] | TE [%] |
---|---|---|
23,090,500.45 | 85.897 | 90.09 |
Dead storage in 2013 [m3] | Dead storage in 2023 [m3] | Dead storage change [10 years m3] | Actual Sedimentation Rate [m3·a-1] |
---|---|---|---|
494,712.98 | 155,680.22 | 339,032.75 | 33,903,275 |
Landform | Texture [%] | M | a | b | c | K | ||
---|---|---|---|---|---|---|---|---|
Sand | Silt | Clay | ||||||
River valley | 31 | 37 | 32 | 4,624 | 4.31 | 3 | 4 | 0.39 |
Colluvial plain | 27 | 64 | 7 | 8,463 | 3.12 | 2 | 4 | 0.76 |
Lower slope | 25 | 36 | 39 | 3,691 | 4.05 | 3 | 1 | 0.23 |
Middle slope | 20 | 72 | 8 | 8,464 | 2.62 | 2 | 5 | 0.83 |
Upper slope | 44 | 31 | 25 | 5,625 | 3.86 | 2 | 2 | 0.38 |
Hillcrest | 10 | 20 | 70 | 873 | 4.50 | 3 | 4 | 0.12 |
Slope [%] | Slope classification | Length and steepness LS | Area [ha] | Percentage [%] |
---|---|---|---|---|
5–15 | II | 1.20 | 307.59 | 7.57 |
15–35 | III | 4.25 | 1,178.64 | 29.01 |
35–50 | IV | 9.50 | 1,501.23 | 36.94 |
>50 | V | 12.00 | 1,076.03 | 26.48 |
Total | 4,063.50 | 100.00 |
Land use | C | Conservation management | P | Crop management and soil conservation CP | Area [ha] | Percentage [%] |
---|---|---|---|---|---|---|
Conservation forest | 0.001 | No conservation | 1.00 | 0.001 | 1,373.11 | 33.8 |
Plantation forest | 0.2 | No conservation | 1.00 | 0.2 | 627.66 | 15.4 |
Mixed cropland | 0.1 | No conservation | 1.00 | 0.1 | 957.50 | 23.6 |
Settlement | 1 | No conservation | 1.00 | 1 | 378.06 | 9.3 |
Paddy field | 0.01 | Traditional terraces | 0.40 | 0.004 | 291.32 | 7.2 |
No conservation | 1.00 | 0.01 | 37.92 | 0.9 | ||
Dryland farming | 0.7 | Contour farming (9–20%) | 0.75 | 0.525 | 130.47 | 3.2 |
Contour farming (>20%) | 0.90 | 0.63 | 267.46 | 6.6 | ||
Total | 4063.50 | 100.0 |
Actual | Potential | |
---|---|---|
Dead storage [m3] | 155,680.22 | |
Sedimentation rate [m3·a-1] | 33,903.275 | 309,106.630 |
Remaining useful life [year] | 4.59 | 0.50 |
Rain station | Rainfall erosivity [R] | Area [km2] | R × Area |
---|---|---|---|
Kedungwringin | 2,467.21 | 16.18 | 39,915.92 |
Sampang | 2,437.48 | 18.27 | 44,527.47 |
Sempor | 2,176.53 | 3.85 | 8,390.13 |
Somagede | 2,828.84 | 2.33 | 6,601.82 |
Total | 40.63 | 99,435.35 | |
Rainfall erosivity (R) of the reservoir catchment area [MJ mm ha−1 h−1 a−1] | 2,447.04 |