1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Yes

1.4 Declaration on sustainability of the described Technology

Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?

No

1.5 Reference to Questionnaire(s) on SLM Approaches (documented using WOCAT)

Vu Gia Thu Bon River Basin Information Centre [Viet Nam]

The VGTB River Basin Information Centre (RBIC) offers decision support tools for stakeholders and aims at providing comprehensive information and consulting services to the water and land users according to their demands.

• Compiler: Justyna Sycz
• 07/28/2015 midnight

2.1 Short description of the Technology

Definition of the Technology:

Return flow from paddy fields is strategically collected before being lost to rivers and is reused as an effective source of agricultural water.

2.2 Detailed description of the Technology

Description:

Return flow from paddy fields is defined as applied water that is not lost by evapotranspiration but returns to an aquifer or surface water body (Womach, 2005). The two types of return flow are surface and sub-surface. Surface return flow accounts for the major proportion. If surface return flow is strategically collected before entering rivers, it can be used as an ‘extra’ effective source of agricultural water supply (Phil King, 2008; Simons et al., 2015). Because paddies effectively purify water by absorbing nitrogen and phosphorus, this produces return flow of an acceptable quality for irrigation purposes. Return flow can be collected by drainage canals and stored in ponds and reservoirs, and then returned to pumps for reapplication. This technology offers one solution towards overcoming a deficit of irrigation water.

The goal of this technology is to store and reuse surface return flow from paddy farms to enhance irrigation efficiency. The purpose of constructing temporary barriers in drainage canals is to minimise water wastage and optimise the possibility of collecting and recycling surface return flow. Return flow from irrigation system is stored in surrounding ponds and reservoirs Return flow can only be used when it is captured in a storage structure or drain which has a hydraulic link to the irrigation source: thus an integrated framework for the reuse system consisting of both hydraulic, and management, links should be established. Within the scope of this study, the Water Management Unit (WMU) is understood as an integrated irrigation and drainage system consisting of four components: (i) the hydrological catchment which covers both non-irrigated and irrigated area; (ii) the source scheme generating return flow; (iii) the reuse scheme that is hydraulically connected with the source scheme; and (iv) a drainage system functioning as a harvesting as well as a supply structure.

Before implementing such a system it is recommended to analyse the correlation between irrigation efficiency and reuse of return flow, as well as developing a framework for managing and recycling return flow. Investigation aims at identifying the potential of return flow for irrigation; determining its quantity and quality; and developing an efficient and sustainable reuse framework. Water balance calculations, field measurements, water quality sampling and interviewing are all used for this purpose.

In the study area, long dry seasons cause severe water shortages and problems with saline intrusion. The study area is mainly covered by paddy, vegetables and other annual crops such as maize, sweet potatoes, peanuts and sugarcane. Paddy rice, which consumes a high proportion of the freshwater, is the dominant crop. Agricultural land in the downstream area is irrigated through gravity or pump irrigation systems. Here results indicate that the irrigation efficiency can be improved significantly: the irrigation efficiency of Tu Cau and Thanh Quyt irrigation schemes is projected to increase respectively by 1.8 and 1.4 times.

Reuse of return flow can be applied in all WMUs where the drainage canals are connected with storage tanks. Scientific and technical support tools are offered by the Vu Gia Thu Bon River Basin Information Centre. The centre was established in Danang providing a comprehensive information service to farmers and other water users – it includes capacity building and consulting services also.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

Country:

Viet Nam

Region/ State/ Province:

Quang Nam

Further specification of location:

Dien Ban

Map

×

2.6 Date of implementation

If precise year is not known, indicate approximate date:

• less than 10 years ago (recently)

2.7 Introduction of the Technology

Specify how the Technology was introduced:

• through land users' innovation
• during experiments/ research

3.1 Main purpose(s) of the Technology

• improve production
• conserve ecosystem

3.2 Current land use type(s) where the Technology is applied

Cropland

• Annual cropping
• Perennial (non-woody) cropping
• Tree and shrub cropping

Annual cropping - Specify crops:

• cereals - maize
• cereals - rice (wetland)
• root/tuber crops - sweet potatoes, yams, taro/cocoyam, other

• vegetables

Perennial (non-woody) cropping - Specify crops:

• sugar cane

Tree and shrub cropping - Specify crops:

• tree nuts (brazil nuts, pistachio, walnuts, almonds, etc.)

Number of growing seasons per year:

• 2

Specify:

Longest growing period in days: 130, Longest growing period from month to month: 20th December to 28th April; Second longest growing period in days: 110, Second longest growing period from month to month: 20th May to 06th September

Comments:

Major land use problems (compiler’s opinion): The lowland part of Vu Gia Thu Bon is an intensive agricultural area. Rice cultivation, which consumes a high proportion of fresh water, accounts for 70% of total agricultural land (Ribbe et al., 2011). Since 2005, due to the impacts of droughts and saltwater intrusion, water for irrigation during the dry seasons has become an increasing problem in the lowland area of this basin. Simultaneously, the irrigation efficiency of this region is relative low. Various measures are applied to address water scarcity for irrigation. Reusing return flow is regarded as a potentially new measure to reduce the severity of the irrigation deficit in dry periods.
Major land use problems (land users’ perception): Based on the information provided by the Department of Natural Resources and Environment (DONRE) for Quang Nam Province, this basin now faces the problem of temporarily insufficient irrigation water. This situation is caused by droughts, insufficient reservoir capacity, salinity intrusion and ineffective irrigation management.

3.4 Water supply

Water supply for the land on which the Technology is applied:

• full irrigation

3.5 SLM group to which the Technology belongs

• water harvesting
• surface water management (spring, river, lakes, sea)

3.6 SLM measures comprising the Technology

structural measures

• S5: Dams, pans, ponds
• S6: Walls, barriers, palisades, fences

management measures

• M2: Change of management/ intensity level
• M6: Waste management (recycling, re-use or reduce)

3.7 Main types of land degradation addressed by the Technology

water degradation

• Hs: change in quantity of surface water

Comments:

Main causes of degradation: crop management (annual, perennial, tree/shrub) (Paddy rice requires huge amounts of water. Meanwhile, the coefficient of irrigation return flow from paddy field is also quite high.), industrial activities and mining (Hydropower construction reduces water availability for irrigation), over abstraction / excessive withdrawal of water (for irrigation, industry, etc.) (It causes water waste and reduces irrigation efficiency.), change of seasonal rainfall (It affects the paddy water balance and actual irrigation need.), droughts (It causes saltwater intrusion.)
Secondary causes of degradation: change in temperature (It relates to evapotranspiration.), inputs and infrastructure: (roads, markets, distribution of water points, other, …), governance / institutional

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:

• reduce land degradation

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

Methods of recycling return flow from paddy fields: The surface return flow can be captured by drainage canals and stored in tanks: return water from these reservoirs is pumped back into irrigation canals.
In 2012, the first on-farm irrigation structure was initially implemented in the Tu Cau WMU in order to use return flow for irrigation purposes. The existing Sen Pond was enlarged and a temporary pumping station was installed to pump water into the irrigation canal system.
According to the pumping diary of Tu Cau station (in Winter-Spring crop 2013), there were totally 7 irrigation periods (8-11 days/period). Total input water (including effective rainfall) during the measuring period from 01 March to 10 April was about 28,000 m3. Meanwhile the total volume of return flow of the Tu Cau site was 16,176 m3. This amount of return flow has the potential to irrigate the agricultural area for about 16 days, equivalent to one and a half irrigation periods. The overall efficiency of the irrigation system will be significantly improved.
Location: Lowland area of VGTB Basin. Quang Nam Province
Date: January 2014

Technical knowledge required for field staff / advisors: high
Technical knowledge required for land users: low
Main technical functions: water harvesting / increase water supply

Dam/ pan/ pond
Depth of ditches/pits/dams (m): 2
Width of ditches/pits/dams (m): 194.9
Length of ditches/pits/dams (m): 399.4

Wall/ barrier
Height of bunds/banks/others (m): 0.5
Width of bunds/banks/others (m): 0.25
Length of bunds/banks/others (m): 1.26

Construction material (other): Stone, sandy bags and bamboo sticks
Specification of dams/ pans/ ponds: Capacity 116764.59m3
Catchment area: 77860 m²m2
Beneficial area: 30 ham2
Other type of management: Return flow is the part of drainage flow, it is necessary to enhance the institutional link to develop the reuse framework for the study area. Think about reforming IMC to IDMC with D is drainage.

Author:

Trinh Quoc Viet

4.2 General information regarding the calculation of inputs and costs

other/ national currency (specify):

VND

If relevant, indicate exchange rate from USD to local currency (e.g. 1 USD = 79.9 Brazilian Real): 1 USD =:

20828.0

4.3 Establishment activities

4.4 Costs and inputs needed for establishment

Comments:

Duration of establishment phase: 12 month(s)

4.5 Maintenance/ recurrent activities

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Prices of the material and equipment; the approval procedure and disbursement process of the project of “Dredging and expanding Sen Pond”; the compensation cost for the farmers; the cost of operating and maintaining temporary pump; the cost of reinforcing the drainage canals.

5.1 Climate

5.2 Topography

5.3 Soils

5.4 Water availability and quality

5.5 Biodiversity

5.6 Characteristics of land users applying the Technology

Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly common / average land users
Population density: > 500 persons/km2
Annual population growth: 1% - 2%
1% of the land users are very rich and own 3% of the land.
2% of the land users are rich and own 7% of the land.
70% of the land users are average wealthy and own 60% of the land.
25% of the land users are poor and own 20% of the land.
2% of the land users are poor and own 10% of the land.
Off-farm income specification: There is a large industrial park located near the study site and a large part of the working population in the region is earning income by working in the factories.

5.7 Average area of land used by land users applying the Technology

5.8 Land ownership, land use rights, and water use rights

Land ownership:

• state

• farmer, individual

Water use rights:

• open access (unorganized)

• farmer, individual

5.9 Access to services and infrastructure

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

Water availability and quality

Other socio-economic impacts

Socio-cultural impacts

Ecological impacts

Water cycle/ runoff

Soil

Other ecological impacts

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change

Climate-related extremes (disasters)

Meteorological disasters

Climatological disasters

Hydrological disasters

Other climate-related consequences

Other climate-related consequences

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?

6.5 Adoption of the Technology

Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?

• 51-90%

Comments:

By applying the technology, the potential reuse area of return flow is estimated about 33% of the study area (30.4ha of agricultural area is potentially irrigated by return flow). However, estimating the number of land user families that have implemented the technology is not the initial aim of the study. Therefore, it requires further detailed investigation and social survey as well.

6.7 Strengths/ advantages/ opportunities of the Technology

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Kim, H. K. et al. (2009) Estimation of irrigation return flow from paddy fields considering the soil moisture

Available from where? Costs?

Agricultural Water Management, 96(5), 875–882.

Title, author, year, ISBN:

Phil King (2008) Return Flow Efficiency

Available from where? Costs?

New Mexico Water Resources Research Institute

Title, author, year, ISBN:

Simons, G.W.H. et al. (2015) Water reuse in river basins with multiple users: A literature review

Available from where? Costs?

Journal of Hydrology. 558–571

Title, author, year, ISBN:

Ribbe et al. (2011) Annex 2 to Milestone Report 2011 - Description of the Study Region including an updated stakeholder analysis,

Available from where? Costs?

LUCCi project. ITT, Cologne University of Applied Sciences