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

No	Station	Coordinates		Length of record		Elevation	Month Rainfall
		Latitude	Longitude	Length of record		Elevation	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

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.

Table 2

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

No	Station	Homogeneity			Normality
No	Station	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

[i] Significant (S) and Non-significant (NS).

Table 3

Test statistical analysis results for monthly rainfall erosivity.

No	Station	Eq. Regression			Spearman's Rho		Mann Kendall		Trend
No	Station	r²	β₁	β₀	r_s	Z_sr	s	Z_s	Trend
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

* – statistically significant trend level (α = 0.01).

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.

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.

Table 4

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

No	Station	Eq. Regression			Spearman's Rho		Mann Kendall		Trend
No	Station	r²	β₁	β₀	r_s	Z_sr	s	Z_s	Trend
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

* – statistically significant trend level (α = 0.01).

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.

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DOI: https://doi.org/10.2478/quageo-2021-0028 | Journal eISSN: 2081-6383 | Journal ISSN: 2082-2103 (formerly 0137-477X)

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Language: English

Page range: 125 - 142

Submitted on: May 23, 2021

Published on: Sep 30, 2021

Published by: Adam Mickiewicz University

In partnership with: Paradigm Publishing Services

Keywords:

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© 2021 Supriyono Supriyono, Sugeng Utaya, Didik Taryana, Budi Handoyo, published by Adam Mickiewicz University
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 40 (2021): Issue 3 (September 2021)

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

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Table 1

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Table 2

Table 3

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Table 4

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