Estimating the Useful Life of the Sempor Reservoir Using Erosion Modelling

Satrio Budiman; Slamet Suprayogi

doi:10.14746/quageo-2024-0004

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Estimating the Useful Life of the Sempor Reservoir Using Erosion Modelling

Quaestiones Geographicae

Volume 43 (2024): Issue 1 (March 2024)

By: Satrio Budiman and Slamet Suprayogi

Open Access

|Jan 2024

Figures & Tables

Agricultural activities around the inlet of the Sempor Reservoir.

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

Table 1.

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

Table 2.

Parameters for sedimentation rate formulation.

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

Table 3.

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

Monthly rainfall erosivity of the Sempor Reservoir Catchment Area.

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).

Table 4.

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

Landform	Texture [%]			M	a	b	c	K
Landform	Sand	Silt	Clay	M	a	b	c	K
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

Table 5.

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

Table 6.

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
Paddy field	0.01	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
Dryland farming	0.7	Contour farming (>20%)	0.90	0.63	267.46	6.6
Total					4063.50	100.0

Parameters used in estimating erosion potential with the USLE model.

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

Table 7.

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

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

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

Table 8.

Monthly discharge of the Sempor Reservoir.

Month	Monthly discharge [mln m³ · month^-1]
Month	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

Table 9.

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

Table 10.

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

Table 11.

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

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DOI: https://doi.org/10.14746/quageo-2024-0004 | Journal eISSN: 2081-6383 | Journal ISSN: 2082-2103 (formerly 0137-477X)

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Language: English

Page range: 63 - 78

Published on: Jan 20, 2024

Published by: Adam Mickiewicz University

In partnership with: Paradigm Publishing Services

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© 2024 Satrio Budiman, Slamet Suprayogi, published by Adam Mickiewicz University
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 43 (2024): Issue 1 (March 2024)

Estimating the Useful Life of the Sempor Reservoir Using Erosion Modelling

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