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Estimating the Useful Life of the Sempor Reservoir Using Erosion Modelling

Satrio Budiman
Satrio Budiman
 und 
Slamet Suprayogi
Slamet Suprayogi
   | 20. Jan. 2024
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Online veröffentlicht: 20. Jan. 2024
Seitenbereich: 63 - 78
DOI: https://doi.org/10.14746/quageo-2024-0004
© 2024 Satrio Budiman et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Fig. 1.

Agricultural activities around the inlet of the Sempor Reservoir.
Agricultural activities around the inlet of the Sempor Reservoir.

Fig. 2.

Study area. Legend for land cover: 1 – conservation forest, 2 – plantation forest, 3 – mixed cropland, 4 – settlement, 5 – paddy rice, 6 – dryland farming.
Study area. Legend for land cover: 1 – conservation forest, 2 – plantation forest, 3 – mixed cropland, 4 – settlement, 5 – paddy rice, 6 – dryland farming.

Fig. 3.

Monthly rainfall erosivity of the Sempor Reservoir Catchment Area.
Monthly rainfall erosivity of the Sempor Reservoir Catchment Area.

Fig. 4.

Landform map and soil sampling points in the Sempor Reservoir Catchment Area. Explanation: yellow squares marked soil samples, landforms: 1 – river valley, 2 – colluvial plain, 3 – lower slope, 4 – middle slope, 5 – upper slope, 6 – hillcrest. Data source: field survey and laboratory analysis by Fitryady (2008) and Rachma (2019).
Landform map and soil sampling points in the Sempor Reservoir Catchment Area. Explanation: yellow squares marked soil samples, landforms: 1 – river valley, 2 – colluvial plain, 3 – lower slope, 4 – middle slope, 5 – upper slope, 6 – hillcrest. Data source: field survey and laboratory analysis by Fitryady (2008) and Rachma (2019).

Fig. 5.

Parameters used in estimating erosion potential with the USLE model.
Parameters used in estimating erosion potential with the USLE model.

Fig. 6.

Annual erosion rate distribution in the Sempor Reservoir Catchment Area using the USLE model.
Annual erosion rate distribution in the Sempor Reservoir Catchment Area using the USLE model.

Fig. 7.

Echo sounding measurement points to record the depth of the Sempor Reservoir.
Echo sounding measurement points to record the depth of the Sempor Reservoir.

Fig. 8.

Depth contour of the Sempor Reservoir interpolated using empirical Bayesian kriging.
Depth contour of the Sempor Reservoir interpolated using empirical Bayesian kriging.

Distribution of erosion susceptibility in the Sempor Reservoir catchment.

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

Monthly discharge of the Sempor Reservoir.

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

List of data used in this study.

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

Parameters for sedimentation rate formulation.

Parameter Equation
Trap efficiency TE [%] TE=96.67+(17.82×(lnCI))+(0.569×(lnCI)2)1+(0.154×(lnCI))+(0.0153×(lnCI)2)$${\rm{TE}} = {{96.67 + (17.82 \times (\ln {{\rm{C}} \over {\rm{I}}})) + (0.569 \times {{(\ln {{\rm{C}} \over {\rm{I}}})}^2})} \over {1 + (0.154 \times (\ln {{\rm{C}} \over {\rm{I}}})) + (0.0153 \times {{(\ln {{\rm{C}} \over {\rm{I}}})}^2})}}$$
Sediment yield G [t·a-1] G = SDR × Ea

Trap efficiency (TE) of the Sempor Reservoir.

Reservoir capacity [m3] Annually discharge [mln m3 · a-1] TE [%]
23,090,500.45 85.897 90.09

Actual sedimentation rate of the Sempor Reservoir.

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

Soil erodibility (K) in the Sempor Reservoir Catchment Area.

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

LS classification in the Sempor Reservoir Catchment Area.

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

CP in the Sempor Reservoir Catchment Area.

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

Estimated remaining years of the useful life of the Sempor Reservoir.

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

Rainfall erosivity (R) in the Sempor Reservoir Catchment Area based on rainfall weighting.

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
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