Water management in poldered areas,case of the Red River Delta
By: Dang The Phong

Abstract: It's well known that technologies for water resources utilization vary from one
region to another due to the variability of natural and socio-economical conditions. In
order to contribute to the generalization of water management practices, this paper deals
firstly with physical and institutional characterization of polders1 operation in the Red
river delta. Secondly, problems associated with polders management will be summarized
to show challenges that this style of rearrangement for water utilization faces.

1. Introduction
The Red river delta (RRD), situated in the North of Viet Nam, is the second agricultural regionof the country, after the Mekong Delta in the South. Cultivation together with water resources
utilization of the delta has practiced for centuries. However, the extensive introduction ofmodern technologies for water control began only during the French colonial occupation anddeveloped recently, in the late 50’s, in an effort to ameliorate the agricultural production
conditions. Physical facilities and institutional arrangements in the delta actually presents one
distinguished style for water resources utilization in delta areas, said "water management inpoldered areas". Its characteristics allow conveniences and oppositely, cause several problems to
management activities. Providing an overall vision about polders operation is what this synthetic
paper intends to partake.

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In this paper, a polder refers to a single area completely surrounded by the dikes of the rivers and/or the sea. In the

RRD, there are 30 polders with the total area varying from 5 000 to 200 000 ha (cf. Figure 1). Equipments for
irrigation and drainage of polders constitute a single hydraulic systems. From hydrological point of view, the 30
hydraulic systems of the delta are independent to some extent as they are directly supplied by adjacent river reaches
in irrigation period and directly discharged to them in drainage period.

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In this objective, the paper will begin with the brief introduction to the RRD, emphasizing those
properties that lead to understand water management principles in the delta. Functioning ofpolders will be followed in the second and the third paragraph and, main problems related topolders exploitation will be stated in the last.

2. Generalities of the RRD
The RRD is a plain of approximately 12 500 km2, 7 210 km2 of which is for agriculture. The
delta is originated by alluvial deposed by the Red and the Thai Binh rivers, both flowing in a
direction from north-west to south-east. These two parallel rivers and their branches, sometime
connecting one river to another, constitute a dense hydrographical network of the delta.
It’s firstly important to note that the average annual flow of the rivers is so significant that itpresents an abundant water resource for the delta. At the entry of the delta, the average annual
flow for a period from 1856 to nowadays of the Red river alone 2 is roughly 3600 m3/s,
accounting for an annual arriving volume of 113 billion m3. However, water regime of the rivers
strongly varies according to seasons, from 368 to 34 320 m3/s in dry and rainy seasons
respectively. One of reasons is that river flow is poorly controlled as there are only two
significant storage reservoirs in the upstream, the Hoa Binh and the Thac Ba with live storage
capacity of 5.6 and 1.2 billion m3 respectively.
Secondly, it’s worth also to mention that the Red river is said to be one of the most dangerous
rivers in the world as the water table is rather steep and may raise very high. Even for thedownstream reaches in the delta, it varies from 0.022 to 0.102 m/km, equivalent to the watertable descent of 2.2 to 10.2 m for a distance of 100 km. In rainy season, water level at the central
delta may be superior than land level of several meters. Moreover, water level might fluctuate
rapidly depending on rainfall in the upstream of the basin.
Belonging to as said south-eastern Asian monsoon massive, the RRD climate is characterized byseasonal variations. In the summer, the monsoon winds associated with tropical storms move2

Data for flow of Thai Binh river is not reliable due to the back water effect.

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westward from the South China Sea. In the winter, the dry and cold winds come from the centerof Asia.
The annual rainfall distribution over the delta is fairly uniform and averages 1740 mm.
However, it’s unevenly distributed over the shorter time period. The dry months from November
through April contribute an average of only 200 mm and the wet months from May throughOctober contribute 1500 mm. When viewed on a daily time period, rainfall is much lessuniformly distributed. Some drought may occur during the rainy season, even on a year withaverage total annual rainfall and heavy storms may account for several hundreds of mm in one to
five days when tropical storms or tropical barometric depressions occur. That's why rainfall
would be sufficient to satisfy crop water requirements in most years, but due to the highly
nonlinear temporal distribution of rain, most runs off and cannot be retained in the polders.
Similarly, other climatic factors vary according to seasons: humidity, evaporation from open
water surface, temperature are high in summer and low in winter.
The topography of the DFR is dominated by the general slopping direction from north-west to
south-east. The relief is low, varying between the sea level and the isometric curve of 10 m,
72 % of its total surface being inferior of 2,5 m. However, natural land elevation is rugged
because of the presence of dikes “that prevent rivers ... to fill up the topographical depressions”.
In a certain cultivation blocs of 1000 ha, differences between the lowest plot and the highest plot
may reach 5 m.
The RRD has a population of 17 million. It is one of the most densely populated regions in theworld with many rural areas supporting 1000 persons/km2. Since most of the rural population is
occupied with rice-based cultivation3, the high demographic density has called for an urgent
need for irrigation and drainage introduction to allow intensive cultivation. However, agricultural
production has dramatically developed only from 1988 to present, under the policy of the3

The cropping pattern of about 70% of cultivated area composes of spring rice from February to June and summer

rice from July to October. The rest 30% are occupied by spring rice, summer rice and winter upland crops(vegetable, potato, maize, etc.) from November to January.

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decentralization and privatization movement known as Doi Moi. The operation and managementof the irrigation systems is also evolving rapidly at all levels; from the development of central
control and authority to the local and self-sustaining management enterprises. Agricultural
diversification is also one important feature of these period. Others cropping patterns such as
rice-fish, valuable cash crops year-round replace rice-based cultivation.

3. Description of polders
The hydraulic systems of polders is based on the same technical model that composes of threecomponents: (i) the primary gravity network, (ii) the irrigation units and, (iii) the drainage units.
The description of polders that follows will start with brief characterization of the threecomponents and finish with explanation of how they operate together.
3.1. Primary gravity network
Reaching all over the polder, the primary gravity network serves the dual purpose: it provides
water sources for numerous irrigation units and receives waters excesses extracting fromdrainage units. In addition, it plays a role as a receiving body for wastewaters of urban andindustrial areas in the polder. Thus, this network can be considered as a intermediary of rivers
and irrigation and drainage units.
The primary gravity network consists of a main channel and a big number of branch channels (cf.
Figure 2). For a large polder, the length and the width of the main channel may be as big as 100
km and 100 m respectively, and total length of branch channels bigger than 10 m of width may
reach several hundreds of kilometers.
This primary gravity system involves one or more intake gates and one or more outlet sluices to
let water transfer into or out of the polders. However, there are only one intake gate and one
outlet sluice for a polder in most cases. The big gates in the delta can be as large as several tensof meters. To gain from big water table gradient and to facilitate irrigation and drainage at thesame time, the intake gates are situated in the upstream of the polder where water level of river ishighest and drainage sluices in the downstream where water level is lowest.

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There are also water control sluices on the primary gravity system to divide the network into
several independent reaches.
3.2. Irrigation unit
In irrigation period, the polder is divided into a large number of irrigation units, each of which isserved by one pumping station or one turnout depending on whether it’s irrigated by pumping orby gravity. Command area of irrigation units varies from several tens of hectares to more thanten thousands of hectares and averages 150 hectares.
Due to low water level in the primary gravity system, irrigation by pumping is dominated (70 to
80% of total arable land). According to the technical norm, pumping stations are designed for adelivery capacity of about 1 litter/second/hectare. After a period of multiplication of pumping
stations from 1988 to present however, delivery capacity is actually much more important. It
may reach 7 l/s/ha in many cases.
In common situation (more than 75% of total arable land), irrigations units are served by the
primary gravity system, meaning that their pumping stations or their turnouts are scattered along
the main channels and its branches. Others are independent units not covered by the primarygravity system. They are supplied directly by rivers, through pumping stations or turnouts
situated along the main dikes.
In each irrigation unit, there exists one distribution network consisting of elevated irrigation
canals and control devices, which plays a role to deliver water to all plots in the unit.
3.3. Drainage unit
Similarly to the irrigation period, the polder is divided into a large number of drainage units
which are drained to the primary gravity system or directly to rives through pumping stations oroutlets along the gravity system or river dikes. Inside each drainage unit, there’s one network ofdrains which plays a role to collect water excesses from cultivation plots as well as villages andconvey them to the unit’s pumping station and/or outlet. Even in the case of drainage by
pumping, the drains systems are usually arranged so that the water can also drain by gravity
through the primary system when the river levels are low enough to permit this. As the volume5

of water to be drained in whatever time period is bigger than that to be delivered in irrigationmode, infrastructures for drainage purpose are designed with high capacity, from several l/s/ha tomore than ten l/s/ha.
To terminate the description, it’s important to pay an attention to following remarks.
-

Limits of irrigation units rarely coincide with that of drainage units. One irrigation unit
might composes of several drainage units and vice versa. In general however, the numberof drainage units is smaller than that of irrigation.

-

Some of the pumping stations are configured so that they can serve both irrigation anddrainage functions. In these cases the number of pumps served for irrigation is usuallysignificantly smaller than that for drainage.

3.4. Operation of polders
The polders can be said to be primarily operated in either a irrigation mode or a drainage modeat any given time. However, both functions may be served simultaneously during much of atypical period. To easily describe the operation principles of polders, irrigation and drainage
modes are distinguished.
•

In the irrigation mode

In the irrigation period, the main intake gate is opened to feed the primary gravity system withwaters available in the river and the outlet sluices are closed to store water in the polder.
Sluices along the main channel are justified to maintain differently water levels in different
reaches to meet the irrigation demands of different zones, which are normally different due to theelevation variability of landforms. Moreover, they help share water deficits between different
zones when water level in the river is too low.
Available water in the primary gravity network is elevated by pumping stations and thendistributed all over the irrigation units by the delivery networks. When irrigation by gravity ispossible, turnouts are open to allow gravity flow from the primary gravity system to plots.
•

In the drainage mode

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During drainage period, water flows in inverse direction. Water excesses in drainage units areaccumulated in drains and then extracted to the primary gravity system by pumping stations oroutlets. The main intake gates are closed to prevent river waters penetrating in the gravity
network and main outlet sluices are opened to drain water out to rivers whenever it’s possible.
The main control sluices are opened too to maximize the flow in the primary gravity system.
It’s important to note that water level in the primary gravity system may rise higher than land
elevation due to the high water level in rivers. That’s why the primary gravity network is
associated with secondary dikes both sides.

4. Institution for water management
There are two parallel organisms involving in water management: ‘administrative’ and‘technical’. While administrative organisms deal with policymaking, technical organisms are
responsible for system operation, maintenance. They are both hierarchically organized from
central to local levels and have different tasks.
4.1. Administrative organisms
Function of administrative organisms is based on administrative boundaries such as state,province, district, commune.
They are headed at the central level by the Department of Water Resource belonging to the
Ministry of Agriculture and Rural Development. The department is responsible for issuing
relevant documents related to water management (rules for the calculation of the water fee, water
laws, etc. for example) and approving the implementation of major projects (planning, design,
construction and funding).
At provincial level, the Water Resource Service belonging to Provincial Office of Agriculture
and Rural Development provide policy advice (setting the provincial water fee based on nationalguidelines), decides on investments for small intervention projects and provides subsidies fortechnical organisms when needed.

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At local level, from district to commune, specified organisms are assigned to oversee whether
issued guidelines and decisions are respected and whether irrigation and drainage services are
performed as intended.
4.2. Technical organisms
After the construction of system is accomplished, infrastructures are handed over to technicalorganisms to exploit them. Unlike administrative organisms, they are functioning on either
natural or administrative boundaries.
On large polders which embrace more than one district, one Irrigation and Drainage
Management Company (IDMC), a state company, is established to manage (operate, maintainand financial manage) the primary gravity system, including the main intake gates, drainage
sluices and control sluices. The management of infrastructures at lower level such as branches ofthe primary gravity system, centralized pumping stations, principal irrigation canals and drains isdesignated for District Irrigation and Drainage Management Companies (DIDMC), a statecompany too 4. There may be more than ten DIDMC under the IDMC in one polder in samecases. While IDMC functions in a basic of areas or zones having natural boundaries (polders),
DIDMC is based on district boundaries.
On small polders which embrace only one district, IDMC doesn't exist and DIDMC is
responsible for all tasks from water source creation in the primary gravity system to pumping
station and then principal secondary canals.
At local level, cooperatives are the last formal technical organisms who are involving in water
management. Their main task is to receive water delivered by DIDMC then distribute it to allparcels and to maintain field canals. When there are local pumping stations, cooperatives have tooperate and maintain their system from the pumping station down to the fields.
Since late 1980s, all above mentioned technical organizations are expected to act as selfsustaining management enterprises, meaning to cover their water source creation, irrigation and
4Centralized pumping station is defined as those which are constructed by Government and managed by statecompany. In contrary, local pumping is those which are constructed and managed by local communities.

8drainage services, and maintenance costs through the collection of a water fee paid by farmers.
Water fee is divided into three parts: (i) water sources creation in the primary gravity system(said also water fee for water source creation), (ii) irrigation and drainage costs, including
pumping expenditure and maintenance of related channels (said also water fee for irrigation anddrainage) and, (iii) water distribution and canals maintenance at field level (said also field waterfee). The payment is carried out bottom up from farmers to IDMC and each organisms keep therelevant parts to spend for their activities. In common situation, the cooperatives keep the fieldwater fee, the DIDMC the water fee for irrigation and drainage and IDMC the water fee forwater source creation. When there are local pumping stations, cooperatives only pay for water
source creation and drainage costs and keep irrigation fee for themselves.

5. Problems related to polders management
Although contributing to agricultural production development, experiences from the last 50 yearsof exploitation show that this style of water management encounters some obstacles that restrict
its potential service capacity. There are still unsolved technical, economical and institutional
problems that challenge the sustainability of the systems. The analyses of key issues related tosystem operation that follow will demonstrate this statement.
5.1. Integration of scales
We have seen that the polders components are physically hierarchical and operate in interaction.
To ensure the efficiency of system operation, all the components should be technicallycompatible. However, it's not the case in the reality.
In all polders, the primary gravity system and its branches rest almost unchanged since thecreation of the system from late 1950s. Additionally, sedimentation deposing in their beds
significantly decreases its conveyance capacity. Whereas, many pumping satiations have been
additionally constructed. This situation leads to technically dysfunction of the system.
In irrigation period, newly constructed pumping stations at the tail-end of braches of the primarygravity network can’t operate normally because available water is utilized by others situated in
the upstream. In drainage period, multiplication of pumping station makes the primary gravity
9network overloaded. Water excesses extracted from drainage units is hardly withdrawn to therivers. Water level in the network may raise so high that managers have to stop pumping stations
to avoid overflowing and to close outlets of drainage units which are drained by gravity to avoid
water penetrating in the units. It’s then more convenient to examine the needs for upgrading the
primary gravity system and the need to construct more pumping stations.
5.2. Optimization of system operation
It’s obvious that an application of appropriate operation rules potentially increases the
exploitation efficiency of any kinds of systems. For the complicated system like the polders, thelarge size or the important system inertia, the mixed utilization for both irrigation and drainage
purposes, the heterogeneity of the system, the rapid evolution of irrigation and drainage units,
and the unpredicted variability of climatic and hydrological conditions etc. prevent managers tounderstand how the system would respond to different operation options. In other words, theelaboration of optimum solutions for polders operation is a sophisticated problem so that theheuristic methods that are actually applied can’t handle. Statistics show different situations
where water deficits or waterlogging are caused not only by severity of climatic conditions nor
limitation of system’s physical capacity but also by inappropriateness of systems manipulation.
Failure to share water sources for irrigation during water shortage period and to use effectively
storage capacity of units in drainage period is an example demonstrating the statement. Other
example concerns the operation solutions to meet contradictory service purposes. The strategy tomaintain low water level in the primary gravity system during rainy season in order to facilitate
the drainage, without considering that the storage capacity of the system is negligible incomparison with the rain, has historically caused water stress in rainy season when water isabundant.
Thus, identification of adaptive solutions for systems operation is one of technical difficulties
associated with the complexity of the polders.
5.3. Organization of irrigation and drainage units

10The operational schema of polders hasn’t changed for the last 50 years, since the creation of
hydraulic systems. However, it’s not the case for the organization of irrigation and drainage units.
Regarding to irrigation and drainage, the polders evolution can be divided into two principal
periods:- From system creation to 1980: this period, well known as a period of modernization andcollectivization of production, is marked by construction of large irrigation and drainage units
associated with capacitive pumping stations. The command area of some units may reachseveral tens thousands hectares.
- From 1980 to present: during this period of the promotion of decentralization, many small
pumping stations are additionally constructed inside the existing command area of big
pumping stations. Other large number of capacitive pumping stations are installed along themain dike, that convert units initially drained to the primary gravity system into independent
units drained directly to rivers. As a result, irrigation and drainage channels and some pumpsof big units are no longer used.
The mentioned situation of fragmentation of large irrigation and drainage units show theuncertainty of definition of irrigation and drainage units. Thus, a question of how to determine
their size and their organization to adapt to managerial and physical conditions is still unsolved.
5.4. Water quality management
Hydraulic systems of polders don't include a separate sewerage network to drain out wastewaters
coming from cities, industrial centers, handicraft villages. All kind of wastewaters are discharged
in the primary gravity networks of polders, dispersed all around the networks, and then reusedfor irrigation in combination of available fresh water. Untreated wastewaters contain high levels
of inorganic and toxic substances, and dangerous pathogens. Severe direct and indirect impactsof water pollution to communities health and agricultural production have been reported, notably
in polders that embrace densely agglomerations and important industrial centers.
Theoretically, application of infrastructure or operation measures to increase the assimilation
capacity of water receiving bodies can help minimize pollution impacts. Unfortunately, no11measures have been sufficiently considered in reality. Thus, due to the polders configuration,water quality management is one of major challenges to improving irrigation water.
5.5. Institutional issues
Institutional problems relating to water management in polders include difficulties to (i) ensure
economical sustainability of technical organisms involved in water management and (ii) to share
responsibilities between them.
We have seen that technical organisms involved in water management have to cover theiroperation and maintenance cost by collected water fee. However, it's reported that almost all ofthem lack of financial sources to maintain the systems as well as needed. They fall in a vicious
cycle: lack of financial source to maintain the systems leads to systems deterioration, leading tohigh water loss, leading to high operation cost (electricity expenditures), leading to lack offinancial sources. From technical point of view, the main issue is that different irrigation anddrainage units are commonly served by the primary gravity system. Even in rainy season when
the water level in rivers is much more higher than field levels, water level in the primary gravity
network has to be maintained not too high to avoid unexpected "artificial inundation" for low
laying units and to minimize the storage in order to facilitate the drainage that may be eventuallynecessary. In drainage period, pumped waters from drainage units make water levels in the
primary gravity system so high that drainage by gravity is rarely possible. That’s why irrigation
drainage is normally carried out by pumping even though gravity irrigation and drainage istheoretically possible. It’s then interesting to consider possibility to expand irrigation by gravity
to minimize electricity expenditures.
We have seen that water management tasks is assigned to different operational organisms at
different scale, due to the large size of polders. While the whole hydraulic system of polders
technically function in communication, the operational organisms are completely independent indecision making. In this case, a smooth circulation of information between users in thedownstream and decision makers in the upstream is necessary. Unfortunately, it’s not easy torealize due to the lack of technical means. The IDMC controls the primary gravity system by
12their experiences, without consulting DIDMC about their demands. Another problem comingfrom the splitting of managerial tasks is that there may exist complicating factors due to thedivergence of operational objectives of different organisms. The first example is that while the
district who operates the pumping station tends to minimize electricity expenditures, another
district who is responsible for delivering wants to receive as much water as possible. The second
example is that there may exist no man areas. Many parts of the primary gravity system is badly
maintain because the task is assigned to districts companies, who is not profitable frommaintenance works, rather than to cooperatives, whose pumping cost and production conditions
depend on the conveyance capacity of the channels. Thus, we can conclude that physicalcomplexity of the polders may produces difficulties in solving institutional problems.

Conclusion
The example of water resources utilization in the Red River Delta suggests three topics forfurther discussions.
First topic relates to collectivization against individualization of water management. At deltascale, the abundance of water sources allow to create independent polders, unlikely other delta
where irrigation of the whole delta depends on a common water source (reservoir in the upstream
for example). As a consequence, there’s less technical nor institutional problems coming fromresource competition and coordination for water sharing. At polder level in contrary, thecollective mode for irrigation and drainage of a large number of units provoke not only technicalbut also institutional problems. The discussion in the last chapter demonstrate this statement. It’sthen convenient to consider whether maximizing of individualization of water management ispreferable.
The second topic is the compatibility between technical and institutional dimensions of water
management. Ineffective exploitation of polders due to the lack of appropriate operational rules,
historical fragmentation of irrigation and drainage units in the polders because the technical plan
isn’t suitable to managerial capacity, and deterioration of infrastructures due to the inappropriate
institutional framework can be considered as examples demonstrating this statement.
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Lastly, it’s seemingly interesting to create necessary conditions allowing all decision makers,
stakeholders and users to discuss about identification of problems and possible solutions. We
have seen that not all of above mentioned problems come from the severity of natural conditions.
The failure to asses the needs for upgrading the primary gravity system instead of multiplicationof irrigation and drainage units is a typical example of misunderstanding of overall operation ofpolders.

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Figure 1: Layout of 30 polders of the Red River Delta
24

22
23

21
15

3

30

14
River

17

2
4

1

13

20

sea

16 My Duc
17 Thuy Nguyen
18 Tien Lang
19 Vinh Bao
20 An Thuy
21 Bac Duong
22 Song Cau
23 Nam Yen Dung
24 Soc Son
25 Lien Son
26 Nam Ninh Binh
27 Bac Ninh Binh
28 Yen Lap
29 Uong Bi
30 Dong Trieu

28

19 18
16

tern

1 Bac Hung Hai
2 Nam Thanh
3 Chi Linh
4 An Kim Hai
5 Kim Mon
6 Bac Thai Binh
7 Nam Thai Binh
8 Bac Nam Ha
9 Nam Ninh
10 Nghia Hung
11 Xuan Thuy
12 Hai Hau
13 Song Nhue
14 Phu Sa
15 Ba Vi

29

5

6

27

8

7
9

26

Ea s

25

11
12

10

0

Km

50

Figure 2: Schematization of hydraulic system of a polder
River
Dike
Gravity system
Irrigation canalDrainage channel
Intake gate
Control sluice
Outlet sluice
Pumping station

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