Abstract: Background and Objective: The rapid development of agriculture and settlements has led to several land conversion and one of such affected locations is upstream of the Siak watershed in Riau Province, Indonesia. Land degradation occurs due to soil erosion, which may cause flooding and drought. Therefore, this study aimed to analyze the factors causing erosion and determine how to control it. Materials and Methods: The survey method of observing and measuring soil samples, vegetation and soil conservation techniques applied in each land unit was used. Rainfall data, soil characteristics, slopes, crop management and soil conservation techniques were collected and analyzed using USLE. Results: The results showed that the erosion in the Siak watershed is relatively high (339 tons/ha/year). Furthermore, the plant management and soil conservation techniques did not follow the required principles and the erosion control was determined by improving crop management and soil conservation techniques in an integrated manner at each unit of land. This step was expected to reduce erosion in the Siak watershed. Conclusion: The erosion control in open land areas resulting from clearing need to get top priority. Guidance in the form of counseling and specifically regarding the soil conservation method needs to be carried out earlier and in stages to all landowners.
INTRODUCTION
A watershed is topographically bound by mountain ridges that hold and store rainwater and then channel it to the sea through the main river. Watershed is composed of natural resources (land, water and vegetation), used by humans. When human activities utilize natural resources exceedingly above its carrying capacity, environmental balance will be damaged. These conditions provide a great opportunity to convert potential land into critical land in watersheds. Critical land, due to environmental disturbances has often been associated with the watershed area and it can threaten the land and water resources sustainability. Research result1, stated that watershed has a holistic approach to an ecosystem and climate change adaptation. Therefore, the community role in its management is very necessary. Furthermore, research2 stated that watershed management is not an easy job. It faces challenges such as obtaining adequate participation from the community and difficulty in implementing planning.
Riau Province has four main watersheds, which are Rokan, Kampar, Indragiri and Siak. The Siak watershed is entirely in the Riau Province area, because its scope covers only a few regencies/cities in Riau Province, while the other three cover the provinces of West Sumatra, North Sumatra and Riau itself. The upstream area of the watershed is very important, as it performs the function of ensuring protection for the other parts. Often, it becomes the focus of management planning, given that the upstream and downstream systems have biophysical links through the hydrological cycle. However, the watershed area has shown a decline in its quality. This is mainly due to the development of community socio-economic activities such as plantations, industry, fisheries and sand excavation along the upstream river. Until now, the oil palm plantations have developed in the Siak watershed area. Research3 stated that there has been a shift in land use from rubber plantations to oil palm farming in the upstream area or especially with slopes above 15%. This activity has a high contribution to the erosion hazard level because plantation development activities are carried out by the community without regard to good land management. Other studies4, showed that the development of oil palm plantations causes a land conversion, which could potentially be erosion. Furthermore, it is stated that it has the potential to disrupt the environmental balance, especially in the upstream of the river5.
The plantation area in the upper watershed reaches 466,782 ha and it causes high erosion hazard there. This increased rate of erosion results from differences in slope. Land degradation potentially occurred due to large-scale conversion. Besides, the practice of burning by farmers and plantation developers is also a trigger of land degradation and its association with large soil erosion increases the level of mud along the river, which is indicated by its murky color, especially during the rainy season. Research stated that land use in high slope areas has the potential for erosion. Environmental conservation and recovery practices are needed to reduce the acceleration of the entire process6. Assessed the average potential of annual soil erosion rates, its conversion classes combining with land use, land cover changes in the periphery of highlands, undulating and lowland basins using Revised Universal Land Lost Equation (RUSLE)7.
Land use and impacts on erosion in watershed areas have been performed. Watersheds from semiarid are more sensitive to hydrological processes and the sustainability of water resources than humid areas. Therefore, it is very important to pay attention to the watershed response to the upstream hydrological process8-10. High sloping barren land contributes to the relatively high level of soil loss11. Excessive soil erosion causes a deposited hyper reservoir. This reservoir plays an important role in resisting soil erosion12. Examining the level of erosion in the mining area, the slope of the mine has a great potential to cause erosion by water13.
The level of erosion hazard not only disrupts the ecology but also has an impact on the economic activities of the community. The construction of ecological security patterns is one important way to reduce the contradiction between economic development, ecological protection and the construction of ecological civilizations. It is important to build the ecological security pattern of small-scale countries and achieve sustainable economic development based on the protection of the ecological environment14,15.
Understanding the economic value of land is very important in promoting stakeholder participation for its sustainable use and efficient management. Stakeholders' perceptions are very useful in designing and implementing sustainable land use and management initiatives16-18. Plantation activities have increased the mobility of goods in the villages, causing plantation activities to also open business and employment opportunities for people who could accept these opportunities19.
There is a trade-off between economic development and environmental conservation. Plantation development will have consequences for forest and land conservation20. Economic factors influence the mapping and management strategies for the emergence of conflicts in the Siak watershed21. The implementation of Sustainable Livelihood Approaches (SLAs) can reduce erosion and vulnerability in watersheds. Synergy provides guarantees for the lives of local people22. Ecological economics has emerged as a coherent transdisciplinary approach to solving environmental problems23.
Before this research, there has not been an integrated effort by the relevant agencies and the community in controlling the watershed from damage. Therefore, erosions need to be investigated. The objectives of this study are (1) to determine the location, area and level of land criticality to figure out the method, type and priority of handling; (2) to analyze the effect of plantation development and erosion-causing factors and (3) to determine erosion control methods for each land unit in the Siak watershed.
MATERIALS AND METHODS
Study area: This research was conducted in the Siak watershed. The study focused on the upstream area of the Siak River with an area of 466,782 ha. Upstream is a watershed area with hilly and bumpy topography. Conduct research from April-October 2018.
This research uses a survey method by observing and measuring in the field. The survey was conducted using the development method. Observations were made on the soil and vegetation of each land unit contained in the plantation development area. Measurements were made of the slope, height from sea level and soil depth on each land unit according to the work map. To obtain general information about the condition of potential areas to be developed, this research uses a lot of primary data obtained through surveys.
Materials and tools: This research uses the survey method and data collected include both primary and secondary data (Table 1). The materials used were a land cover map of Landsat imagery, topographic maps with a scale of 1:50,000, geomorphological maps with a scale of 1:25,000 and location maps with a scale of 1:50,000. The tools used include compass, meter, hoe, shovel, ground drill, Abney level and GPS.
Statistical analysis: The magnitude of erosion (A) is determined by the Universal Soil Loss Equation (USLE) proposed24. USLE calculation techniques are widely applied throughout the world, especially in watersheds research, as previously performed25,26. An integrated modeling approach to determine the spatial and temporal dynamics of erosion susceptibility27. Soil erosion has been considered a major cause of soil degradation, soil erosion causes loss of soil organic matter which is essential for plant growth28. Effective soil erosion modeling to identify areas most vulnerable to soil loss, manage and minimize the impact of degradation29. To the regional scale, soil erosion is the main reason for soil degradation in mountainous and highland areas in Vietnam. The soil in Tay Nguyen loses productivity due to erosion30,31. The following equation presents a better explanation:
A = R×K×LS×C×P |
where, A is the magnitude of soil loss per unit area per year (tons/ha/year), R is rainfall erosivity factor (mj.cm/ha/h/year), K is soil erodibility factor (ton/ha/mj.cm/ha/h), L is slope length factor, S is slope factor, C is factor in how to farming or grow crops and P is factor of soil conservation action.
The R-value was obtained from the EI30 rainfall Erosivity predictor index using the Lenvain equation32:
R = 2,21 (Rm) 1,36 |
Rm represents the average monthly rainfall (cm) because it is the following available data.
| Table 1: | Data types, measured variables and data collection methods | |||
| Data Type | Parameter | Unit |
Data collection methods | Data source |
| Rain (R) | Rainfall | cm |
Erosivity analysis | BMKG (Meteorology, climatology |
| The day of rain | Day |
and geophysics agency), Pekanbaru | ||
| Slope (LS) | Length | m |
Topographic map analysis | Bakosurtanal (National Coordinating |
| The Slope | % |
Agency for Surveys and Mapping), Bogor | ||
| Land (K) | Permeability | cm/h |
Laboratory observations and analysis | Field |
| Depth | cm |
|||
| Organic matter | % |
|||
| Structure | - |
|||
| Texture | - |
|||
| Content weight | gr/cm3 |
|||
| Vegetation (C) | Land use | - |
Analysis of satellite imagery, land | Field and LAPAN (National Institute of Aviation |
| Soil Processing (P) | Conservation techniques | - |
coverage maps and field observations | and Space), Jakarta |
| Soil | ||||
The K-value is determined based on texture, structure, permeability and content of organic matter in each soil sample, which is included in the nomograph. Furthermore, the C-value is determined based on a C factor value table for several types of plants in Indonesia. The P-value is determined according to the P factor value table for several soil conservation techniques. The LS factor is determined using the equation33, where LS is the length and slope factors, λ is slope length (m) and S is the slope (%):
RESULTS AND DISCUSSION
Use of plantation land in the watershed area: Based on the survey, there is a significant imbalance in the land tenure system (Table 2). People who own very small land are generally residents who work outside the agricultural sector. They are poor people with limited capital and resources, cannot open new land. They have livelihoods as farm laborers both on smallholder plantations and on large private plantations. In general, they only have a yard of land and housing. On the other hand, residents who have large tracts of land generally move in the plantation sector, especially oil palm farming.
Communities with very large Lands are living in transmigration villages and residents participating in the community nucleus estate (PIR) and Primary Cooperative Credit for Members (KKPA) programs. In the autonomy era, the right of local people to control land is greater. However, this right is always based on ulayat unilateral recognition or other customary rules that have not been recognized by the government. The rights owned by residents are often used to control state land, to sell them to migrants. Most respondents in the survey stated that they have privately owned land (81.78%), even though only a small proportion could present certificates from the National Land Agency (BPN). Only a small portion of the population rents land; even the ownership system is not found in rural areas. Agricultural activities are performed by the community on their land for plantation, food crops, horticulture and a small portion is used for residential land.
Oil palm plantations are the most extensive form of agricultural land use in the upstream area of Siak watershed. It was developed by many independent and large private companies. Most residents have converted their rubber plantations into oil palm plantations which can be harvested 2 times a month, starting at 4-25 years.
| Fig. 1: | The Oil palm land clearing in the survey location |
| Fig. 2: | Land conditions in the Siak Watershed |
Therefore, the permanent agricultural business is influenced by residents in this area. The rejuvenation is carried out when the production results are declining, then the farmers will immediately remove all oil palm trees and replant, both simultaneously and in stages. As Fig. 1 is a form of palm plantation rejuvenation activity. At present most of the oil palm plantations have begun to be rejuvenated to enter the second cycle. The oil palm plant cycle is 25-30 years. The condition of the Siak watershed area that already open has been shown in Fig. 2. The rapid development of oil palm plantations results in increased land use. Most of the Siak watershed has already taken over the function of land from forest to oil palm plantations. Research related to land use change34, changes in land use from forests to agricultural systems results in land degradation and conflicts between residents. The conversion of land into plantation land has the potential to erode.
Land cultivation begins with clearing (land clearing) and followed by making planting holes. Its management is not evenly distributed throughout the plantation area, but only around the planting point through holes.
| Fig. 3: | Map of erosion hazard levels (TBE) in Siak Watershed |
| Table 2: | The area of land ownership by sample communities in the upstream of Siak Watershed | |
| Classification | Population |
Percentage |
| Very small (<0.25 ha) | 53 |
24.77 |
| Small (0.25-0.50 ha) | 10 |
4.67 |
| Moderate (0.50-0.75 ha) | 9 |
4.21 |
| Wide (0.75-1.00 ha) | 16 |
7.48 |
| Very wide (>1,00 ha) | 126 |
58.88 |
| Total | 214 |
100.00 |
| Table 3: | The area and proportion of erosion hazards (actual erosion) in the upstream of Siak Watershed | ||
The magnitude |
Proportion |
||
| Erosion hazards class | of erosion |
Area (Ha) |
(%) |
| I | <15 ton/ha/th |
179,371 |
38.40 |
| II | 15-60 ton/ha/th |
123,039 |
26.40 |
| III | 60-180 ton/ha/th |
70,964 |
15.20 |
| IV | 180-480 ton/ha/th |
20,205 |
4.30 |
| V | >480 ton/ha/th |
71,559 |
15.30 |
| Water body | - |
1,644 |
0.40 |
| Total | 466,782 |
100.00 |
All existing natural vegetation is cleared and burned at the land clearing stage and it is considered very vulnerable to soil erosion due to the condition of open land without protection. Land clearing for palm oil is carried out by the community without regard to the condition and slope of the land. Even done at a level of up to 15%. Communities without going through the process of land conversion to open land for plantation business in protected forest areas. The results of research in the Kaligarang watershed35, apart from the biophysical characteristics of socio-economic factors such as lack of awareness of soil erosion and low income affect the level of erosion danger.
Erosion hazard level: Results of the erosion hazard in the upstream area of Siak watershed showed a high increase. In the past 15 years, the actual weighted erosion rate of 29 tons/ha/year increased to 339 tons/ha/year. The rate of change is in the category of hazard class IV (180-480 tons/ha/year). Its continuity greatly threatens the sustainability of the area. Table 3 shows the proportion of erosion hazards in the Siak Watershed at Riau Province.
Results of the Erosion Hazard Level (EHL) aspects show that there are serious sedimentation problems. In 2005, the EHL condition was very heavy and it covered only 0.05% of the total watershed area. However, in 2018, there was a large increase in EHL, reaching 15% of the total area. Therefore, the emergence of sedimentation along the river influenced erosion in the upstream. In more detail, EHL is presented in Table 4 and the distribution map in Fig. 3. Efforts to reduce the potential for erosion must be done in the form of counseling and increasing public knowledge.
In sloped areas, changes in land use from forests to agricultural systems result in land degradation and erosion potential. The community must be encouraged to do a more sustainable planting system especially for farmers in hilly areas. Grass fodder strips (GFS) are effective anti-erosion practices and involve lower costs for farmers34. Soil erosion has the potential to reduce agricultural productivity. On the other side, it has an impact on economic losses in terms of agricultural production and gross domestic product (GDP). Loss of crop productivity (physical changes in crop production) has an impact on a country's agricultural sector36.
Location and area of erosion control target: Biophysically, in the Siak watershed, the location of erosion control activities are based on the value/class of hazards (from moderate to very severe categories). Some locations are presented in Fig. 4 and 5. Meanwhile, from the socio-economic aspect, erosion control activities are focused on areas with high population pressure (>1).
High erosion hazard values indicate the need to immediately carry out erosion and sedimentation control activities. The location targets immediately handled are 164,501 ha or 35.24% of the upstream watershed area. The treatment types and forms in erosion control activities are presented in Appendix 1, while the target activities are presented in Fig. 6.
The results of conservation activities in the Siak watershed are expected to reduce the rate of erosion from an average of 1,252.70 tons/ha/year to an allowable erosion rate of 14 tons/ha/year. Furthermore, the surface area of vegetation can be increased by these activities because there is a pattern of annual and perennial crop farming. Previous findings suggested this will increase the pressure discharge. The direction of land conservation activities in the watershed area can maintain the continuity of water supply in the area.
The land productivity in the Siak watershed area is greatly affected by the direction of each recommended conservation activities. It will continuously affect farmers' income from the agricultural sector, under each type of activity. When the average surface area of agricultural land for each farmer to live properly was 2.50 ha, then it would provide income to farm families of 1,800-2,000 $/farmer/year (transmigration and plantation standards). Therefore, the level of farmer's income is above the poverty threshold.
Furthermore, conservation activities can reduce the value of population pressure on land in the watershed area. Finally, it can reduce the costs required to create awareness, especially in terms of farming activities permanently and not damage the surrounding forests.
| Table 4: | Erosion hazard levels in the upstream of Siak Watershed | |||
| 2005 | 2018 | |||
| Erosion hazard level | Area (Ha) |
% |
Area (Ha) |
% |
| Very slight (<15 ton/ha/th) | 222,683.79 |
45.88 |
179,312 |
38.41 |
| Slight (15-60 ton/ha/th) | 73,922.92 |
15.23 |
121,326 |
25.99 |
| Moderate (60-180 ton/ha/th) | 179,737.36 |
37.03 |
71,319 |
15.28 |
| Severe (180-480 ton/ha/th) | 8,827.94 |
1.82 |
21,622 |
4.63 |
| Very severe (>480 ton/ha/th) | 236.14 |
0.05 |
71,559 |
15.33 |
| Water body | - |
- |
1,644 |
0.35 |
| Total | 485,408.15 |
100 |
466,782 |
100 |
| Fig. 4: | The Siak watershed area that changes |
| Fig. 5: | The observation of Siak watershed area |
| Fig. 6: | Map of Erosion Hazard Control at Siak Watershed |
As an economic activity, it cannot be separated from external influences, both on the biophysical and socio-economic environments, identified from an increase in growth centers to improve service functions.
Soil erosion in developing countries poses threats to rural livelihoods, the sustainability of the agricultural sector and the environment37. The evaluation study of socioeconomic benefits is intended to obtain an idea of how much the benefits level of conservation activities is assessed from the comparative advantage toward regional development. Therefore, the identification and assessment of their relationship should be carried out effectively and it can be identified by the net income of the socio-economic aspect.
Similar to other sector development activities, conservation is expected to have positive or beneficial external influences on the surrounding area. The benefits to the socio-economic aspects are (1) Expanding employment and business opportunities; (2) Increasing the welfare of the surrounding community; (3) contributing to regional development.
Some conservation activities that will directly influence the socio-economic and cultural components of the surrounding community are (1) Agroforestry, reforestation activities and others; (2) Forest village community development; (3) Expansion of infrastructure facilities, utilized by local communities; (4) Absorption of local labor; (5) Agricultural, health and education counseling.
The upstream river plays an important role, such as providing water to the downstream area for agricultural, industrial and residential purposes, as well as maintaining the ecological balance for life support systems. As the dominant production factor, they often experience conflicts of interest in land use for agricultural, tourism, mining, settlement and others. Researchers38 stated that soil loss from watersheds in intensive agricultural activities is 20 times greater than at peak rainfall levels. Forest canopy cover with a higher infiltration capacity reduces erosion runoff. Therefore, soil loss can be reduced, provided good agricultural practices are encouraged.
As a result of several activities, downstream areas are usually misused and negatively affected. However, to maintain the natural balance and water cycle, forest vegetation should be well-managed. On the contrary, the presence of forests in the upstream areas are influenced by land-use patterns related to community behavior, hence interests should also be included as a key factor in the management policies.
| Appendix 1: | Conservation recommendations in the Siak Watershed Area | |||||
The Number |
Area per |
Area per |
||||
| Administrative Region | Activity type | Activity description | of Location |
Area (Ha) |
Sub-district. |
Regency |
| Kampar regency | ||||||
| Bangkinang Sub-district | V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, | 20 |
6.114 |
6.114 |
|
| Grass Barrier/Alley Cropping, Terrace | ||||||
| Bangkingan Barat Sub-district | V1, V2-T1 | Reforestation, plant enrichment, retaining Dam | 3 |
241 |
||
| V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 1 |
14 |
|||
| V4, V6-T1 | Reforestation, community forest, retaining DAM | 18 |
567 |
|||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 19 |
1.632 |
2.454 |
||
| Cropping, terrace | ||||||
| Kampar Sub-district | V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 5 |
1.119 |
1.119 |
|
| Cropping, terrace | ||||||
| Tambang Sub-district | V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 1 |
112 |
112 |
|
| Cropping, terrace | ||||||
| Tapung Sub-district | V1, V2-T1 | Reforestation, Plant enrichment, Retaining DAM | 30 |
9.628 |
||
| V1, V2, V4-T1 | Reforestation, Plant enrichment, Greening, Retaining DAM*) | 20 |
538 |
|||
| V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 69 |
10.673 |
|||
| V4, V6-T1 | Greening, Community Forest, Retaining DAM | 9 |
592 |
|||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | |||||
| cropping, Terrace | 113 |
28.178 |
49.608 |
|||
| Tapung Hilir Sub-district | V1, V2-T1 | Reforestation, Plant enrichment, Retaining DAM | 5 |
901 |
||
| V1, V2, V4-T1 | Reforestation, Plant enrichment, Greening, Retaining DAM*) | 38 | 1,758 |
|||
| V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 45 |
23,309 |
|||
| V4, V6-T1 | Greening, Community forest, Retaining DAM | 6 |
737 |
|||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 62 |
12,673 |
39.378 |
||
| Cropping, Terrace | ||||||
| Tapung Hulu Sub-district | V1, V2-T1 | Reforestation, Plant enrichment, Retaining DAM | 10 |
845 |
||
| V1, V2, V4-T1 | Reforestation, Plant enrichment, Greening, Retaining DAM *) | 6 |
229 |
|||
| V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 25 |
9.065 |
|||
| V4, V6-T1 | Greening, Community forest, Retaining DAM | 8 |
933 |
|||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 70 |
17.654 |
|||
| cropping, Terrace | ||||||
| XIII Koto Kampar Sub-district | V1, V2, V4-T1 | Reforestation, Plant enrichment, Greening, Retaining DAM*) | 1 |
167 |
28.894 |
|
| V1, V3,V11-T1 | Reforestation, HKm, AUK, Retaining DAM | 1 |
29 |
|||
| V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 1 |
10 |
|||
| V2-T1 | Plant Enrichment, Retaining DAM | 1 |
10 |
|||
| V4, V6-T1 | Greening, Community forest, Retaining DAM | 1 |
14 |
64 |
127.743 |
|
| Rokan hulu regency | ||||||
| Kunto Darussalam Sub-district | V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 2 |
75 |
||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass Barrier/Alley | 13 |
1.519 |
1.595 |
||
| Cropping, Terrace | ||||||
| Rokan IV Koto Sub-district | V1, V2, V4-T1 | Reforestation, Plant enrichment, Greening, Retaining DAM*) | 1 |
5 |
||
| V2-T1 | Plant enrichment, Retaining DAM | 13 |
1.553 |
|||
| V4, V6-T1 | Greening, Community Forest, Retaining DAM | 4 |
103 |
2,267 |
||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass Barrier/Alley | 3 |
605 |
|||
| cropping, Terrace | ||||||
| Tandun Sub-district | V1, V2-T1 | Reforestation, Plant enrichment, Retaining DAM | 2 |
106 |
||
| V1, V2, V4-T1 | Reforestation, Plant Enrichment, Greening, Retaining DAM*) | 5 |
1.61 |
|||
| V1,V3,V11-T1 | Reforestation, HKm, AUK, Retaining DAM | 1 |
222 |
|||
| V2-T1 | Plant Enrichment, Retaining DAM | 27 |
983 |
|||
| V4, V6-T1 | Greening, Community forest, Retaining DAM | 18 |
2.404 |
|||
| V6-T1 | Community forest, Retaining DAM | 10 |
1.906 |
|||
| V6, V7-T1 | Community forest, Agroforestry, Retaining DAM | 1 |
6 |
|||
| V7, V8, V9-T1 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 4 |
658 |
|||
| cropping, Retaining DAM | ||||||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass Barrier/Alley | 24 |
3.166 |
|||
| Cropping, Terrace | ||||||
| Kabun Sub-district | V1, V2-T1 | Reforestation, Plant Enrichment, Retaining DAM | 15 |
729 |
11,788 |
|
| V1,V3,V1-T1 | Reforestation, HKm, AUK, Retaining DAM | 5 |
464 |
|||
| V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 2 |
24 |
|||
| V4, V6–T1 | Greening, Community Forest, Retaining DAM | 21 |
1.875 |
|||
| V7, V8, V9-T1 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 8 |
518 |
|||
| cropping, Retaining DAM | ||||||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 70 |
13.202 |
16.083 |
31.732 |
|
| cropping, Terrace | ||||||
| Siak regency | ||||||
| Minas Sub-district | V1, V2–T1 | Reforestation, Plant enrichment, Retaining DAM | 6 |
410 |
||
| V1, V2, V4-T1 | Reforestation, Plant enrichment, Greening, Retaining DAM*) | 5 |
2.976 |
|||
| V1,V3,V11-T2 | Reforestation, HKm, AUK, Terrace | 1 |
21 |
|||
| V4, V6–T1 | Greening, Community forest, Retaining DAM | 4 |
1.064 |
|||
| V7, V8, V9-T2 | Agroforestry, Wanatani/Wanafarma, Grass barrier/Alley | 5 |
529 |
5 |
5 |
|
| cropping, Terrace | ||||||
| Pekanbaru city | ||||||
| Rumbai Sub-district | V1,V3,V11- T2 | Reforestation, HKm, AUK, Terrace | 1 |
26 |
26 |
26 |
| Total | 164.501 |
|||||
| V1: Reforestation,; V2: Plant enrichment, V3: HKm (community forest), V4: Greening, V6: Community forest, V7: Agroforestry, V8: Wanatani/Wanafarma (Agroforestry), V9: Grass Barrier/Alley Cropping, V11: AUK, T1: Retaining DAM, T2: Terrace | ||||||
The allocation of upstream land resources for development purposes should be based on the accuracy of water catchment calculations including physical characteristics, existing land use, community interests and commitment towards sustainable development; the allocation of these resources is closely related to spatial use planning. Therefore, good spatial planning should consider the efficiency of land resources to optimize their interests. Research result39 stated that rainfall affects the hydrological flow due to the conversion of primary forests to agriculture. The open land in the upstream area has the potential to increase erosion. The previous research results40, showed the effects of forest harvesting in watersheds tend to increase the volume of water, which is further responsible for erosion in the slope.
The watershed management and utilization as a planning unit should be based on several considerations, such as (a) a holistic approach; (b) evaluation of the biophysical relationship and intensity of social, economic and cultural activities between upstream and downstream; (c) evaluation of environmental influences more easily and precisely; (d) a function of an area. Research by Castro stated that social service assessments can be used for watershed management and planning considerations in the future41. Gifford42, watershed management is a coordination of all activities that affect the preservation of the natural resources to function optimally, sustainably and efficiently. Furthermore, it is an integrated effort in the utilization, structuring, maintenance, supervision, control and restoration of the functions of land and water resources, rivers, surrounding areas and community intervention42.
Soil erosion in watersheds has become a threatening problem for agricultural production. Policy interventions are needed to reduce erosion hazards in better conservation planning by considering the class of priority areas43. There is a need for conservation and management actions by policymakers that can be applied in watershed areas44. Watershed management is a river basin development concept, which is continuous with a sustainable process. Therefore, it requires coordination and integration between cross-sectorial agencies and regional governments. The institutions involved have a function in the arrangement, regulation, utilization, prevention and control.
CONCLUSION
Most farmers in the Siak watershed have limited ideas about vegetative conservation. They cultivate the land without considering the sloping topography. This behavior has an impact on increasing erosion rates in the Siak watershed area. Erosion control is determined by changing or improving crop management and integrated conservation techniques on each unit of lands, such as reforestation, plant enrichment, Community Forest (HKm), reforestation, community forests, agroforestry (wanatani/wanafarma), grass barrier/alley cropping, AUK, small dam and terrace. The location targets immediately handled are 164,501 ha or 35.24%. The erosion control in open land areas resulting from clearing need to get top priority. Guidance in the form of counseling and specifically regarding the soil conservation method needs to be carried out earlier and in stages to all landowners.
SIGNIFICANCE STATEMENT
This research found factors that cause the level of danger of erosion. The main problem causing erosion in the watershed area is plantation business activities that do not comply with land use regulations. The results of the study, the level of danger of erosion in the Siak watershed is already a heavy category. The results of the study are in the form of conservation actions in critical areas that are vulnerable to soil erosion. This research will help researchers to plan reforestation projects in the Siak watershed area. The output of this study is a recommendation to reduce erosion in the Siak watershed. This is expected to be a material consideration for policymakers in controlling and managing watersheds both regionally and nationally.
ACKNOWLEDGMENT
The team is grateful to the Research Institute and Community Service (LPPM) of the Riau University for facilitating this research activity.