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Spatial-Temporal Trend Analysis of Rainfall Erosivity and Erosivity Density of Tropical Area in Air Bengkulu Watershed, Indonesia

Supriyono Supriyono
Supriyono Supriyono
, 
Sugeng Utaya
Sugeng Utaya
, 
Didik Taryana
Didik Taryana
 et 
Budi Handoyo
Budi Handoyo
   | 30 sept. 2021
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Publié en ligne: 30 sept. 2021
Pages: 125 - 142
Reçu: 23 mai 2021
DOI: https://doi.org/10.2478/quageo-2021-0028
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© 2021 Supriyono Supriyono et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Fig. 1

Spatial distribution of mean annual rainfall and stations used for calculating the rainfall erosivity and the erosivity density (ED) in Air Bengkulu watershed.
Spatial distribution of mean annual rainfall and stations used for calculating the rainfall erosivity and the erosivity density (ED) in Air Bengkulu watershed.

Fig. 2

The boxplots indicate the trends for rainfall and rainfall erosivity related to the monthly models. Its's displayed in figure rainfall (blue), rainfall erosivity (red) in the Air Bengkulu watershed.
The boxplots indicate the trends for rainfall and rainfall erosivity related to the monthly models. Its's displayed in figure rainfall (blue), rainfall erosivity (red) in the Air Bengkulu watershed.

Fig. 3

Map of monthly rainfall erosivity in the Air Bengkulu watershed (same range from 66 MJ · mm−1 · ha−1 · h−1 · a−1 to >841 MJ · mm−1 · ha−1 · h−1 · a−1) using the IDW interpolation method.
Map of monthly rainfall erosivity in the Air Bengkulu watershed (same range from 66 MJ · mm−1 · ha−1 · h−1 · a−1 to >841 MJ · mm−1 · ha−1 · h−1 · a−1) using the IDW interpolation method.

Fig. 4

The boxplots indicate the trends for erosivity density (ED) as the ratio of rainfall erosivity (interpolated erosivity map based on IDW) with monthly rainfall data in the Air Bengkulu watershed.
The boxplots indicate the trends for erosivity density (ED) as the ratio of rainfall erosivity (interpolated erosivity map based on IDW) with monthly rainfall data in the Air Bengkulu watershed.

Fig. 5

Map of monthly erosivity density (ED) of the Air Bengkulu watershed (same range from 00.26 MJ · ha−1 · h−1 to > 1.59 MJ · ha−1 · h−1) using the IDW interpolation method.
Map of monthly erosivity density (ED) of the Air Bengkulu watershed (same range from 00.26 MJ · ha−1 · h−1 to > 1.59 MJ · ha−1 · h−1) using the IDW interpolation method.

Characteristics of gauging weather stations used in this study (acc. BMKG Station Class I Pulau Baai, Bengkulu).

No Station Coordinates Length of record Elevation Month Rainfall
Latitude Longitude min max μ σ
[S] [E] Period Years [m] [mm]
1 Anak Dalam −3.70339 102.46 2010–2020 11 149 27 601 256 131
2 Jayakarta −3.815 102.37 2008–2020 13 39 20 763 261 154
3 Merigi Sakti −3.65281 102.4022 2011–2020 10 149 10 854 303 157
4 Taba Penanjung −3.70339 102.5112 2006–2020 15 149 19 773 312 158
5 Karang Tinggi −3.74707 102.4333 2013–2020 8 84 13 717 253 141
6 Pagar Jati −3.60677 102.381 2010–2020 11 136 49 476 249 93
7 RM Liku Sembilan −3.69774 102.5264 2014–2020 7 149 114 478 261 84
8 Tanjung Heran −3.67209 102.5454 2014–2020 7 149 102 550 268 105
9 Taba Teret −3.68685 102.5339 2014–2020 7 149 128 509 261 93
10 Talang empat −3.78407 102.3635 2010–2020 10 30 49 667 257 113
11 Muara Bangkahulu −3.768 102.29 2010–2020 11 30 11 606 231 125
12 Padang Harapan −3.82169 102.29 2011–2020 10 30 6 834 249 156
13 Meteo Bengkulu −3.863 102.328 2011–2020 10 30 5 591 249 143
14 Tanjung Agung −3.79222 102.3204 2010–2020 11 29 23 927 297 176
15 UNIB −3.75894 102.27 2011–2020 10 8.5 16 585 262 143
16 Pulau Baai −3.881 102.308 2006–2020 15 20 14 609 266 136
17 Talang Pauh −3.694 102.25 2011–2020 10 24 11 1033 294 192
18 Disperta Bengkulu −3.81271 102.3061 2016–2020 5 8.5 75 491 247 93
19 Fatmawati −3.85826 102.3368 2011–2020 10 24 5 764 263 156

Test statistical analysis results for monthly erosivity density (ED).

No Station Eq. Regression Spearman's Rho Mann Kendall Trend
r2 β1 β0 rs Zsr s Zs
1 Anak Dalam 0.938* 0.005 −0.698 0.963* 40.427 −436 −0.473 Decreasing
2 Jayakarta 0.879* 0.005 −0.498 0.929* 31.512 −10 −0.381 Decreasing
3 Merigi Sakti 0.911* 0.005 −0.666 0.964* 39.215 147 0.181 Increasing
4 Taba Penanjung 0.937* 0.004 −0.524 0.972* 55.033 416 0.278 Increasing
5 Karang Tinggi 0.969* 0.006 −0.731 0.986* 57.025 28 0.047 Increasing
6 Pagar Jati 0.923* 0.006 −0.668 0.956* 37.012 −69 −0.075 Decreasing
7 RM Liku Sembilan 0.970* 0.005 −0.469 0.989* 60.176 −287 0.612 Increasing
8 Tanjung Heran 0.984* 0.005 −0.643 0.994* 81.788 −147 0.314 Increasing
9 Taba Teret 0.989* 0.005 −0.657 0.993* 75.664 −24 0.053 Increasing
10 Talang empat 0.949* 0.005 −0.680 0.980* 55.934 −104 −0.112 Decreasing
11 Muara Bangkahulu 0.863* 0.005 −0.400 0.949* 34.188 396 0.423 Increasing
12 Padang Harapan 0.881* 0.005 −0.516 0.950* 32.909 137 0.168 Increasing
13 Meteo Bengkulu 0.887* 0.005 −0.455 0.953* 34.024 188 0.321 Increasing
14 Tanjung Agung 0.942* 0.005 −0.716 0.974* 48.831 −29 0.032 Increasing
15 UNIB 0.913* 0.004 −0.505 0.957* 35.684 75 0.092 Increasing
16 Pulau Baai 0.907* 0.005 −0.545 0.961* 46.232 −22 −0.015 Decreasing
17 Talang Pauh 0.795* 0.004 −0.301 0.904* 22.871 151 0.186 Increasing
18 Disperta Bengkulu 0.967* 0.005 −0.592 0.993* 75.664 −19 0.042 Increasing
19 Fatmawati 0.960* 0.005 −0.623 0.978* 50.712 147 0.181 Increasing

Homogeneity test (Bartlett's test) and statistic Shapiro-Wilk's (SW) parametric test on the weather stations.

No Station Homogeneity Normality
Rainfall Rainfall erosivity Erosivity density Rainfall Rainfall erosivity Erosivity density
1 Anak Dalam S NS NS S S S
2 Jayakarta S NS NS S S S
3 Merigi Sakti S NS NS S S S
4 Taba Penanjung S NS NS S S S
5 Karang Tinggi NS NS NS S S S
6 Pagar Jati S NS NS S S S
7 RM Liku Sembilan S NS NS S S S
8 Tanjung Heran NS S NS S S S
9 Taba Teret S NS NS S S S
10 Talang empat S NS NS S S S
11 Muara Bangkahulu S NS NS S S S
12 Padang Harapan S NS NS S S S
13 Meteo Bengkulu S NS NS S S S
14 Tanjung Agung S NS NS S S S
15 UNIB NS S NS S S S
16 Pulau Baai NS S NS S S S
17 Talang Pauh S NS NS S S S
18 Disperta Bengkulu S NS NS S S S
19 Fatmawati S NS NS S S S

Test statistical analysis results for monthly rainfall erosivity.

No Station Eq. Regression Spearman's Rho Mann Kendall Trend
r2 β1 β0 rs Zsr s Zs
1 Anak Dalam 0.971* 3.950 −762.095 0.983* 60.572 −205 −0.223 Decreasing
2 Jayakarta 0.953* 3.021 501.154 0.974* 53.353 993 0.825 Increasing
3 Merigi Sakti 0.948* 3.535 −720.338 0.984* 59.739 303 0.374 Increasing
4 Taba Penanjung 0.964* 2.730 509.743 0.986* 78.670 725 0.485 Increasing
5 Karang Tinggi 0.983* 3.651 −637.470 0.993* 81.075 159 0.090 Increasing
6 Pagar Jati 0.966* 1.975 −553.189 0.981* 57.431 −36 −0.040 Decreasing
7 RM Liku Sembilan 0.980* 2.476 −457.674 0.994* 81.778 −354 −0.754 Decreasing
8 Tanjung Heran 0.990* 2.529 −450.889 0.997* 115.928 −171 −3.65 Decreasing
9 Taba Teret 0.989* 2.509 −449.931 0.997* 115.928 −55 −0.119 Decreasing
10 Talang empat 0.972* 2.998 −529.242 0.992* 89.252 −134 −0.145 Decreasing
11 Muara Bangkahulu 0.921* 2.251 −296.683 0.978* 53.249 713 0.762 Increasing
12 Padang Harapan 0.937* 3.426 −539.441 0.979* 51.945 339 0.418 Increasing
13 Meteo Bengkulu 0.949* 2.832 −440.186 0.978* 50.712 254 0.313 Increasing
14 Tanjung Agung 0.974* 3.740 −726.421 0.988* 72.653 8 0.007 Increasing
15 UNIB 0.962* 2.900 −498.657 0.981* 54.694 182 0.224 Increasing
16 Pulau Baai 0.956* 2.739 −462.022 0.980* 65.519 125 0.083 Increasing
17 Talang Pauh 0.910* 2.640 −431.255 0.962* 38.109 131 0.161 Increasing
18 Disperta Bengkulu 0.971* 2.414 −392.646 0.996* 84.156 −24 −0.053 Decreasing
19 Fatmawati 0.983* 3.422 −585.485 0.990* 75.910 −161 −0.200 Decreasing
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