Joint Circular No. 35/TT-LB on temporary regulations regarding the upper reaches of rivers and streams for flood prevention, flood mitigation, drought limitation, and soil erosion control.

CIRCULAR

JOINT FORESTRY-WATER RESOURCES MINISTRY DECREE NO. 35/TT-LB DATED AUGUST 18, 1980 TEMPORARILY REGULATING THE AREAS AT THE HEADWATERS OF RIVERS AND STREAMS FOR PROTECTIVE PURPOSES TO MITIGATE FLOODS, DROUGHTS, AND EROSION.
DROUGHT, EROSION.

Pursuant to Article 5 of the Decree on the protection of forests; pursuant to Directive No. 278-TTg dated August 16, 1975 of the Prime Minister on the distribution of land between agriculture and forestry;

The two Ministries of Forestry and Water Resources issue this joint decree temporarily regulating areas at the headwaters of rivers and streams for protective purposes to mitigate the effects of floods, droughts, and erosion, referred to as protective headwater areas.

I. THE PROTECTIVE EFFECTS OF FORESTS AND CONSEQUENCES OF DEFORESTATION
OF DEFORESTATION

Forests are part of the living environment and are among the valuable natural resources of our country. Forests provide raw materials for various economic sectors, serve the needs of people's lives, and are important export commodities. Forests purify the atmosphere, enhance the beauty of nature, and have special protective functions in preserving and improving soil quality, retaining water, regulating surface runoff, and mitigating flood and drought damage.

Given that three-quarters of our country's land is mountainous and complex, serving as the source of rivers and streams, forests in these areas are particularly significant for upstream protection.

Research results over recent years have clearly shown:

1. Forests intercept rainwater, retain a considerable amount of water on leaves and in forest litter layers, converting some surface water to groundwater, thereby reducing flood flow volume and lowering peak flood discharge.

2. Forests supplement water to river flows during dry seasons. In practice, river basins fully covered with forests have twice to three times more dry season flow than those without forests or heavily deforested areas. This flow is of great significance for agricultural, industrial production, and people's livelihoods.

3. Forests limit surface erosion, protect and improve soil quality, making water cleaner and forest soil better. Canopy shelters prevent direct rainfall impact on soil, while litter from fallen branches and leaves, along with intertwined roots, obstruct surface runoff, preventing soil erosion and increasing organic matter in the topsoil, making it more porous and fertile.

4. Strips of forests surrounding reservoirs exhibit positive effects in blocking sediment transport, reducing surface evaporation, maintaining, and extending the lifespan of water conservancy projects.

In recent years, droughts and floods have become severe, threatening people's lives and significantly impacting economic development. One of the causes is heavy deforestation. Over the past thirty years, forest area has shrunk considerably. If in 1945, the forest area was 14.5 million hectares, accounting for 43% of the national total land area, by 1975, it had decreased to 9.5 million hectares, representing only 29%. Thus, nearly 5 million hectares of forest were lost. Of the remaining forest area, quality has declined, with rich and medium-quality forests now comprising only one-third, while the rest consists of poor-quality and bamboo forests.

Uncontrolled deforestation has led to higher flood peaks, larger flood volumes, faster flood accumulation, causing severe flooding during the rainy season. During the dry season, river water levels drop, with very low flow rates insufficient to meet agricultural, industrial, and people's daily needs. Severe erosion has resulted in the loss of millions of tons of fertile soil, negatively affecting crop yields. Sedimentation in rivers has complicated riverbeds, reduced the capacity of water storage reservoirs, and in some cases, small reservoirs have been almost completely filled with sediment. Large investments of funds and labor are required annually for drought prevention, flood control, and river dredging.

Flood prevention, drought mitigation, and erosion control have become urgent tasks. One fundamental measure to achieve these goals is to actively protect existing forest areas, quickly restore deforested areas, and accelerate new forest planting, especially in headwater regions. To do this, it is first necessary to promptly determine the forest and forest land areas at headwaters designated for protective purposes, thereby establishing stable protective headwater forests.

For this purpose, this decree initially stipulates certain bases and necessary areas for headwater protective zones.

II. BASIS FOR DETERMINING HEADWATER PROTECTIVE ZONES

Forests have two primary functions: providing timber products and protection. To utilize both functions effectively, it is necessary to reasonably allocate areas for protective forests and commercial forests. Within protective forest areas, although the main purpose is protection, moderate utilization can still be combined without compromising the protective function of the forest. Conversely, in commercial forest areas, attention must also be paid to the protective function.

Currently, there is no specific standard set by the state to determine the size of headwater protective zones. However, based on the urgent requirements stated in Section I, temporary bases for delineating headwater protective zones are provisionally established as follows:

1. Climate.

Our country lies within the tropical monsoon region, significantly influenced by seasonal winds. Annual rainfall is substantial, averaging 1500 to 2000 mm, with some areas exceeding 3000 mm; this rainfall is unevenly distributed, with about 70% to 85% concentrated during the rainy season.

Rainfall is the primary cause of surface runoff and a major factor in erosion and flooding in our country.

AT Areas with high rainfall, receiving significantly more precipitation than the average annual rainfall of the climate zone, should be specially protected and developed with headwater forests to enhance the ability to mitigate flood damage.

2. Topography.

The main topographic factor here is slope gradient.

The slope has significantly influenced and intensified the surface erosion effect caused by rainfall. The steeper the terrain, the shorter the flood concentration time, the faster the flood arrives, leading to more severe erosion and causing serious harm.

Initially, it is proposed that areas with slopes greater than 45 degrees^° be delineated as headwater protection zones and require forest cover to protect the land, limit erosion, and reduce flood damage.

3. For regions with terrain not overly steep (less than 45 degrees)^°or not located in major rainfall areas, but situated at the headwaters of large rivers and streams, especially flat hills in the Central Highlands and southeastern South Vietnam, should also reserve a certain area for headwater protection. The minimum size of this area is defined as 10 to 15% of the natural area of the watershed.

In the designated areas for headwater protection, the canopy coverage must be maintained at 0.7 to 0.8.

4. Forests around water storage reservoirs.

Around water storage reservoirs, there must be a belt of forest to prevent soil and sand from entering the reservoir and to guard against bank erosion and sedimentation within the reservoir. This forest belt must have a width of at least 50 to 150 meters depending on the scale and characteristics of the reservoir.

III. MINIMUM AREA FOR HEADWATER PROTECTION IN WATERSHEDS

Based on the criteria mentioned in Part II above, the minimum area reserved for headwater protection in river and stream watersheds and the locations requiring protection are estimated (attached table).

Minimum headwater protection area of watersheds and locations requiring protection AND THE FORESTRY SECTOR

IV. FORESTRY MEASURES FOR CONSTRUCTING
HEADWATER PROTECTION FORESTS

To mitigate flood damage, regulate flow, and limit erosion, it is necessary to combine agricultural, forestry, and water management measures simultaneously. AT Here, only the functions related to forestry and the measures for constructing headwater protection forests are discussed.

1. For areas with existing forests:

- It is essential to maintain the current forest area in the delineated headwater protection zones of rivers and streams.

For degraded and impoverished forest areas with reduced water retention and soil conservation capacity, they must be designated as restricted zones, and logging, firewood cutting, or excessive exploitation of forest products must be promptly halted.

AT In areas where natural regeneration has not met requirements, seedling planting, afforestation, and forest restoration measures must be implemented.

In areas where forests still produce, logging of forest products must follow established procedures and regulations, avoiding clear-cutting methods, and the harvesting intensity must not exceed the forest's growth rate. AT here the protective function must still be considered as primary.

- Immediate cessation of slash-and-burn practices for shifting cultivation, indiscriminate grazing, and other forms of forest destruction is required, while effective measures to prevent and combat forest fires must also be implemented.

2. For areas without forests:

a. Enclosure and protection:

AT places where the ground cover layer is present but no longer constitutes a forest (large grasslands, shrublands), yet retains its water and soil conservation functions, should be strictly enclosed and fully utilized for the strong regenerative capacity of vegetation to promote forest recovery.

Despite having limitations in terms of speed and time, lacking proactivity, this is a measure with significant economic implications (investment capital, cost, manpower...) that can be applied immediately even in areas not yet suitable for high-level business operations in mountainous regions of the country.

b. Reforestation.

Although it is an active approach, it faces many difficulties due to natural conditions, seedlings, manpower, and capital. Therefore, in the short term, it should only be carried out in critical upstream areas where vegetation no longer has the ability to naturally regenerate into good cover, or near residential areas with favorable conditions for promoting reforestation.

For tree species aimed at protective purposes, long-lived species with good regenerative capabilities, well-developed root systems, numerous branches, and wide canopies should be selected.

V. PROVISIONS ON THE RESPONSIBILITIES OF THE WATER RESOURCES AND FORESTRY SECTORS
AND THE FORESTRY SECTOR

1. Water Resources Departments, based on the grounds stated in Part II, combined with agricultural and forestry production plans and the immediate and future requirements for the water resources sector, propose specific upstream areas to be enclosed for the construction of protective upstream zones, particularly focusing on critical upstream areas. The boundaries, nature, purpose of protection, and requirements to be met for these areas must be clearly defined.

2. Forestry Departments, based on forestry production zoning, their own situation and tasks, and the proposals from the water resources sector, negotiate to reach consensus between both parties on the sites to be designated for the construction of protective upstream forests. Develop a plan for constructing forests that meet the requirements of protective upstream forests.

Subsequently, the two sectors at the local level report to the competent ministry for review and submit to the Government for approval to incorporate into the implementation plan for building protective upstream forests.

The above are some temporary provisions to determine the upstream protective zones of rivers and streams. During the research and implementation process, adjustments and supplements must be made to suit each watershed and locality. When encountering difficulties and suggestions during implementation, units should report to the two ministries for study and resolution.