A full and in-depth study on "Investment in irrigation works in the Mekong Delta" is expected to adopt following 6-point scientific approach:

1. Investment principles and prioritized actions
2. Development and actions
3. Government Resolution 120 on Sustainable and Climate-Resilient Development of the Mekong Delta of Viet Nam and follow-up action plans
4. Agricultural production is over the capacity of the Mekong Delta
5. Prelude to changes
6. Priority policies

However, within the scope of this article which is exclusively prepared for the Vietnam Journal of Agricultural Sciences, the author only focused on the following issues:

Most recently, Ministry of Agriculture and Rural Development leaders put such an interesting question relating to medium term investments in irrigation sector in the Mekong Delta, i.e. which investment is needed to achieve the highest efficiency  and it is very difficult to have correct answer. It is like the idea that someone want to be consulted on which new car they should buy for best performance? Obviously, I can't tell them that they should buy a truck, pickup or a car. With such a What question, we must ask a series of other questions before giving the answer, including why? how? when?

Similarly question to irrigation sector, before giving the answers, the questions will be why and for what purpose? In other words, it is impossible to adequately answer the medium-term question i.e. what should we do, if we do not have our long-term vision and forecast, even our short term goals.

In order to realize the role of irrigation, we have to look at agriculture in different development periods. During the Nguyen dynasty and French Colonialism, irrigation systems are not only for agricultural purposes, rather that lands are reclaimed for building roads and attracting people. During that time, population was small and foodstuff demand was low that and diverting water into fields for rice cultivation for the entire country was not necessary as present.

The irrigation systems at that time are actually integrated systems for socio-economic development, including waterway transportation, residential clusters, agricultural production, fruit planting and aquaculture etc. Later on, we tend to see the Mekong Delta as a granary of Vietnam and thus it is oriented for rice cultivation as the main task and other tasks are underestimated.

We can infer that irrigation work is not the end (salvage) but the means to meet salvage. What is the salvage? I think it is to for sustainable development and in line with the spirit of the Resolution 120 of the Prime Minister issued in 2017.

1. General principles

+ Depending on each ecological sub-region, investment decisions will be made accordingly and properly. Firstly, we have to zone water sources by its functions, land sources and associated ecosystems.

+ Prioritize domestic water supply for medium and low water sources and during arid periods, next priorities will be aquaculture and agriculture.

+ Solutions to protect water resources and restore polluted and depleted water sources.

+ Control river morphology, limit sand mining and prevent river bank and coastal erosion. Sand mining should also adopt the regional connection principles in the Government Decision 593, as the river is an ecosystem and sand mining in some places can affect other areas, including the coast.

+ Develop a water resources monitoring system to record changes in water sources, ecology and livelihoods (both positive and negative changes) of irrigation projects.

+ Proactively respond and warn about risks of upstream water resource exploitation activities (hydropower, incidents of water exploitation projects).

2. Sustainable development

It is necessary to distinguish between growth and development. We have recently overfocused the growth. The 3^rd crop is a good candidate for an example of a growth which is not a sustainable development. Moreover, the development should pay attention not only to the benefits but also to the cost which should be adequately calculated and in a s pecific space (locally, across the delta and nationwide) (now and tomorrow), including the values that cannot be found in GDP reports. Sustainable development must be based on 3 pillars of economic, social, and environmental. Unsustainable development, if any, will pay a price, sooner or later and the recovery cost would be very high.

3. Spirit of Resolution 120

Resolution 120 on Sustainable and Climate-Resilient Development of the Mekong Delta of Viet Nam includes the green growth policy and strategy for the Mekong Delta with a focus on such strategic factors as human resources, science and infrastructure.

From this perspective, 2 important points relating to agriculture must be taken into account

(a) Shifting from traditional agriculture with a focus on quantity to a new one focusing on quality and value chain.

(b) Change the priority: Vegetables, fruit, and rice. I am afraid this transform will be quite difficult. Because aquaculture needs water and aquaculture only can prosper if they can be exported to EU, Japan and the US markets. However, rivers in the Mekong River Delta are now running slowly and they lost their self-purification capacity. They receive a large amount of pollutants from fertilizers, pesticides, contaminated aquaculture and industry.

It is contemplated that the Mekong Delta needs a water-based development strategy. If Resolution 120 wished to transform its existing agricultural structure to seafood, fruit and rice, integrated impacts should be considered and not only export values should be  are taken into account. This rotation of priority axis is rational, yet we should not be deeply involved to move from one extreme to another. In the long run, rice still plays a very important role and it is necessary to reduce intensive farming and pay more attention to quality in accordance with Resolution 120.

As a result, if we want to rotate the priority axis, we have to mention water quality first and then we should (a) transform and reform the agriculture sector (b) clear and recover river flows and (c) enhance environmental management.

4. Irrigation development in Mekong delta after 1975

This is the period of land reclamation and “diverting irrigation water into fields”. This is quite an effective method as only irrigation development can help reclaim lands, deacidify soil, remove alum from soil, expand cultivated area and meet food security needs to reduce hunger nationwide and start the rice export as early as in 1989.

Unfortunately, then we have gone too far with rice and failed to focus on natural values ​​(such as freshwater shrimp, coastal shrimp farming). At that time, irrigation helped optimize rice production through 3 rice crops and enter a new period opposite to before 1995. We have previously opened and then closed since after 1995 up to now. The Delta loses its cushioning ability and becomes less resilient to external impacts. In the dry season, whenever water shortage happened in the Mekong basin, saline intrusion would occur accordingly. To protect the status quo agriculture, we have to dyke to prevent saline intrusion as a result.

5. Necessity of irrigation works

Irrigation works are necessary yet not to protect the status quo at any cost. The problem should be considered in a dynamic state rather than a static state. It is like in the "quintessential archeology" telling the story of a guy who dropped his hammer in the river and marked the dropping location on one side of the boat and rowed it home to ask his friends to dive in and search for the hammer at his marked location on boat’s side. The one who dropped the hammer wanted to find the hammer based on the status quo whereas the boat position has changed. It is referred that irrigation development in the future should not prevent saline intrusion at any cost to protect its existing agriculture in the context of drought and saline intrusion information. It would rather that we should find solutions to achieve the goals set in Resolution 120.

It is necessary to have long-term and integrated strategic thinking on climate change, weather extremes, hydropower dam system, upstream irrigation systems, increased water demands for developments and natural environment, especially the reduced plantation coverage.

The ever developed hydropower and irrigation dam system in the upstream of Mekong river will have a major impact on Mekong river flow, especially in the downstream area. These impacts can be "absorbing flood to reduce flood level in flood season" and "supplying more freshwater to increase low flow in dry season". That is an "eternal" theory to highlight benefits of hydropower dams which are planned, built and operated for the fundamental benefits of the entire river basin, including the Delta. However, this is not likely to be realized in the Mekong river as an international river. By considering hydropower dam system on the Red River (100% owned by the GoV), we can see quite a lot of inadequacies such as difficult regulation of low flow, especially in years with less rains (extreme weather, climate change ..), water storage in reservoirs is not up to design level whereas water demands of different development purposes rise all the time. Only flood absorption is acceptable.

For example, in 2019, there will be a shortage of approx.7.2 billion cubic meters of water which is necessary to regulate low flow in the 2020 dry season for the Red River Delta. Especially, river fisheries have decreased by 70-80%, river alluvia reduced by 40-60%, river bed is lowered, river bank erosion increases, low flows and low water level both deplete and basin-based ecosystems degrade in the delta of Red River Basin.

Particularly, apart from above mentioned impacts, water resources in rivers and canals in the Mekong Delta are also subject to sea level rise impacts due to climate change and land subsidence due to the construction of groundwater works and over-exploitation of groundwater.

6. So what are they?

From a common view and based on actual situation of the Red River basin, it is necessary to have an insight into the Mekong river basin now and in the future so that we can predict and produce forecasts and warnings for irrigation sector (relating to irrigation planning, construction, exploitation etc.) in a more accurate and effective manner.

First of all, it is necessary to define the fixed and flexible boundaries of the 3 regions with different flow regimes i.e. freshwater, brackish water and saltwater. Later on, production planning (for crops, livestock, plants) will be conducted by both irrigation and agriculture accordingly. Finally, how the irrigation work is designed will be decided.

On the other hand, it is necessary to pay special attention to optimal exploitation of specific characteristics (terrain, land and hydrology) of such natural areas as Long Xuyen Quadrangle, Dong Thap Muoi, Ca Mau peninsula, etc. to combine different irrigation planning solutions in a flexible, rational and affected manner without causing unnecessary wastes, overlaps and opposition.

Once the above mentioned requirements are firmly met, we will come to the stage of designing, building and operating respective irrigation systems.

Specific measures are needed to improve water quality, including restricting the discharge of solid wastes into rivers and industrial wastewater to be purified before being discharged into rivers.

1. a) In order to take advantage of both saltwater and brackish water in the coastal areas, we should build proactive saline intrusion control works (two-way sluice gates) rather than desalination sluices. By so doing, people can get water in and discharge water into the sea, with proper wastewater treatment before discharging into the environment. The big problem of coastal aquaculture is wastewater being rotated in different aquaculture ponds.
2. b) Fruit trees in the middle region now are mainly grown using fertilizers due to limited sediment and water exchange with rivers. There are always roads on both sides of any canal or river. The construction of these roads do not take into the ecological processes. Riverside roads are also embankments and they block all flows in and out small canals. A sluice is located every few kilometers. Thus water is not circulated, pollutants are accumulated, soil fertility depletes quickly and fish and shrimp resources deplete rapidly as they cannot move between rivers, canal and fields.

In order to achieve new rural development targets and to prevent flood and protect gardens and orchards, we will create other problems at the same time. If gardens are protected, water will flood other areas and dykes will be built accordingly as a vicious cycle.

To restore the health of lands and rivers in the middle region, such problem must be addressed. However, the solutions are in the hands of provincial irrigation departments and local authorities, other than in master overall irrigation plans.

Currently, for the first time, Vietnam has the Law on Planning 2017 adopting the integration and multi-disciplinary approach. This approach should be thoroughly understood all plans at all levels so that a broader view will be gained to avoid sectoral and local ways of doing things which are to gain several sectoral or local targets rather than to achieve the overall goal.

1. c) In the watershed, semi-dyke structures will be built to protect flood based livelihoods and to control floods during season transitions (for long enough period and reliable for shrimp and fish farming by local people; semi-dykes are also necessary for the 2 rice crops towards clean agriculture. The irrigation system should be clear enough to ensure that soil environment will be flushed and cleaned about for a 10 year period and out agricultural products can reach international markets after that.

For conclusions

Most recently, Prime Minister Nguyen Xuan Phuc clarified the viewpoint of following the nature rule under Resolution 120 which means taking full advantage of natural advantages at the same time building irrigation works at right locations and with proper scale to ensure systematic integration. The construction should ensure that most benefits are gained and least negative impacts are observed together with necessary mitigation measures.

The upcoming 13^th National Party Congress will have new perspectives on all aspects, including those relate to national and regional planning. Investments must be based on plans. All roads must result in the review of disaster management plans and irrigation plans as the prerequisite. For example, the JICA3 Ben Tre project added Tan Phu pumping station in the upstream to supply more water to the entire system during serious saline intrusion period. How the newly constructed Cai Lon-Cai Be sluice system in Ca Mau peninsula is effective and how it affects the long-term development of the Mekong Delta. Following this short-term investment, what must be done for the medium-term to further improve the capacity of the region?

Opinions analyzed in this article are some suggestions of how we can have a long-term vision of irrigation development. These long term visions will be bases for immediate and medium-term steps where priority works will be defined in combination with non-structural measures in the overall sustainable development solution for the Mekong Delta.

These are the author's scientific points of view, not VNDMA’s official opinions