Infrastructure and water management in the Ping Basin

This webpage is a description of the infrastructure built in the Ping catchment and its management by stakeholders. Further information and references can be found in 'Floods and Water Management in Chiang Mai and the Upper Ping Catchment (Pirard, 2025)'.

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FAQ

In the middle of the 20th century, Thailand was granted a World Bank loan for a 25-year irrigation development program that was initiated in 1952. The initial aim was to provide water to the Central Plains to boost rice agriculture outside of the wet season. It started with the building of the Chao Phraya dam in 1957, followed by a series of 5-year plans in the 60s to the 80s with the building of important infrastructure such as Bhumibol Dam (1964), Kiew Lom Dam (1968) and Sirikit Dam (1974) as well as lesser barrages and canals such as the lower Ping dams of Kamphaeng Phet and Nakhon Sawan (1991) and eventually the Upper Ping Weir Project in Chiang Mai Province.

In addition to provide water for irrigation all-year round, these systems also allow regulating water variations downstream and prevent annual minor or intermediate flooding. The effect of the Bhumibol Dam on the Lower Ping is, for example, clearly visible in water level records. While variability in the 1000s of m3/s in Tak existed prior to 1964, it has now an average peak runoff of 240 m3/s with variation around 300±200 m3/s.

Figure 1. Effect of the construction of the Bhumibol Dam (in red, 1964) on the flow variations of the Ping river downstream in Tak. While variations before 1964 are between a few cubic meter per second to 2-3000 m3/s, the construction of the dam maintained a minimum flow >10 m3/s and absorbed most floods below 500 m3/s.

The initial infrastructure was designed for the water management of the Central Plains with some neglect of the consequences on the Ping river basin itself. Changes in sedimentation and water flow in the Upper Ping was modified and from the 70s onwards, the conveyance factor (the ability for the Ping to transport water) was increased and managed through the renovation of flood defenses, dredging and excavation of the river bed upstream of Bhumibol Dam.

Figure 2. Equilibrium profile of the Ping and Chao Phraya river. Blue line is the current river bed topography with black and green dotted line as ideal equilibrium profiles.

In the upper Ping, and Chiang Mai – Lamphun basin particularly, the first permanent infrastructure to manage water were the Pa Ya Kam Weir (1925), Mae Faek Weir (1936) and Mae Ping Gao Weir (1941) but it’s only after all downstream irrigation plans were finished that new weirs and dams were built with Tha Wang Tan Weir (1980), Doi Noi Weir (1987), Pa Ya Utt Weir (1989), Wang Pam Weir (1990), Sob Rong Weir (1993), etc. Since then, some weirs (Tha Wang Tan, Sob Rong) have been upgraded into dams with flood gates to have a better control on water level during the dry season while allowing high flow during floods. All tributaries have also seen a large numbers of weirs and dams built in the last two decades.

Figure 3. Schematic representation of dam and weir infrastructure in the upper Ping river system

To these weirs, major projects have also been built such as the Mae Taeng Weir (1973), Mae Ngat Dam (1985) and Mae Kuang Dam (1991) and the current tunnel project connecting those three.

- The Mae Taeng Project was an early project designed to address water shortages in the uppermost Ping zone and associated with the channel from the ‘canal road’, west of Chiang Mai, that connect the Mae Taeng directly with the Mae Khan in its most recent extension (2024).

- Mae Kuang Dam was already in the plans since 1886, following a major flood but only achieved a permanent dam in 1935, eventually replaced in 1948 by a rock dam and in 1991 by the present concrete structure.

- Mae Ngat Dam like all reservoirs in the area, was originally designed for irrigation purposes but also mitigate floods. The claimed capacity of the Mae Ngat reservoir is to absorb 30% of flood waters passing through Chiang Mai.

Weirs have traditionally been present across rivers in Northern Thailand. In the past century, the muang-fai system (see historical management) has been modernised into concrete weirs and a large number of new ones were added since the 1980s. Their main purpose is to reduce river flow and accumulate water upstream, to maintain a base level in the dry season and be used during droughts. However, during floods, weirs have a detrimental effect as they cause significant obstacles to river flow and inducing a lot of sedimentation on the river bed. These issues have been considered and a number of those weirs are now overhauled into small dams with suitable flood gates.

Water management in the Upper Ping

Dams & reservoirs are very efficient in managing river flow for both dry and rainy season taken separately. In the rainy season, runoff can be retained into reservoirs and released progressively later on, avoiding minor floods and limiting the impact of major floods while in the dry season, water is accumulated and released throughout the season to be available for water consumption. In practice however, water management is made more complicated when considering maximising water storage at the end of the rainy season for the next few dry months while leaving enough volume to absorb large rainfall events occurring in that same end of the rainy season (see weather). During some particularly intense and relatively common rainfall events, reservoirs can reach their capacity and lose their ability to minimize flood volumes.

The whole annual exercise of authorities in Northern Thailand is to find the balance between preserving water for agriculture, irrigation and urban water supply in the dry season, by maintaining the highest possible level in reservoirs at the end of the rainy season, but also ensure that levels are sufficiently low to eliminate the risk of flood downstream. Dry season water management is now benefiting of relatively good prediction of water usage by farmers, supplemented by groundwater extraction (see groundwater). Rainy season management is a lot more of a guessing game due to the lack of sufficiently accurate medium term forecasting of tropical storms or stalling of the monsoon through (see weather), leaving a lot of uncertainty on the best course of action.

In regards to the general characteristics of the Ping river, the presence of dams, weirs and irrigation systems have significantly changed the flow volume. Since the 1960s, the expansion and intensification of agriculture along with the more recent urban-industrial growth and tourism and the end of forest exploitation have changed the catchment and the use of surface water. The irrigable surface has increased from 500 to 2140 km2 between 1972 and 2005, resulting in a drop of inflow in Doi Tao Lake of 0.47% per year over the last 50 years while Chiang Mai and Lamphun see a decrease of 0.28% per year (3.3 mm). Locally, dams also have an impact due to the degradation they cause by accentuating erosion downstream and armouring the riverbed upstream where coarse material is cemented in mud.

Following the catastrophic floods of 2005 in Chiang Mai, the Royal Irrigation Department (RID) expressed its opinion that the cause of extreme flooding was due to encroachment and narrowing of the Ping river and numerous weirs that prevented the water to flow freely. Some weirs were replaced by dams with water gates (Tha Wang Tan in 2013) while others (Chang Klang, Nong Hoi) were left in disrepair. Following the very high level floods of 2024, the removal of additional weirs (maintained or degraded) is again being discussed to improve the conveyance factor of the Ping river during floods.

In 2005, the RID, along with Hydrology and Water Management Centre (HWMC) were allocated 13 billion baht to implement those transformation and including a better monitoring of rivers and warning system and flood preparation but also weir-leveling projects but opposition by local communities for various traditional, practical or cultural reasons prevented the full application of those improvements to the Ping main channel.

The 2005 floods also initiated a serious discussion on the Mae Ngat-Mae Kuang-Mae Taeng diversion tunnel project. The 2011 floods pushed the project forward and it was eventually started in 2015 and is still under construction. The Mae Kuang Udomthara Reservoir Project was started with the Mae Taeng – Mae Ngat diversion tunnel, connecting the two areas with a 4.2 m diameter, 22.975 km long conduit and the Mae Ngat – Mae Kuang diversion connecting the two lakes with a 4 m, 25.401 km long tunnel. Once finished, it will allow to distribute the water from the Mae Ngat reservoir to the other two water systems, with outlets in the Mae Kuang and the Mae Taeng providing some relief on the Mae Ngat outflow into the Ping river upstream of Chiang Mai and optimizing water storage for the dry season.

Figure 4. Schematic plan of the Mae Kuang Udomthara Reservoir Project

Flood prevention & mitigation

Aside from permanent infrastructure and monitoring equipment, a few solutions are provided against flooding and drought.

Dredging is a commonly offered solution to flooding as it lowers the river bed to increase the flow of water. To be effective, dredging would have to be almost an annual process depending on flood conditions but it is unlikely that a budget would be permanently allocated to it in the present administrative structure. Some recent studies on the economic feasibility of such maintenance provided interesting numbers based on the price per cubic meter of river sediments. While prices are too low in the lower Ping (100 THB/m3), it rises to 300 THB/m3 in Lampang, Lamphun and Mae Hong Son and reach 580 THB/m3 in Chiang Mai. Such prices create a positive benefit/cost ratio for dredging which could be economically viable when sediments are repurposed for construction and agricultural nutrients.

The effectiveness of dredging is clearly demonstrated as it provides more volume and less obstacles for water flow. The most obvious numbers are seen when comparing 2005 floods, which despite a record volume flow for the Ping river, had a lower flood level than 2011 or 2024 (see trends and modeling). Politically, dredging is also sought after as it gives the psychological impression to the public that the government is taking action. There are however a few negative impacts associated with dredging towards the ecosystem and ground water. Dredging significantly damage habitats and the large mobilisation of sediment can contribute to river instability. In the dry season, a fully dredged river without appropriate infrastructure can significantly lower the water table and impact irrigation for agriculture.

Figure 5. Ping river catchment with regions where dredging is a potentially economically beneficial process (in red). The highest price for cubic meters of river sediments are found in the Chiang Mai - Lamphun basin.

Bank revetments are made of concrete structure to prevent erosion and flooding when these bank protections are levees. The smooth slab surface also produce higher river flow. Again, they can damage the ecosystem by reducing the environmental values of river banks and in some cases, cause flooding of their own when they narrow the river width producing higher water levels. Along with old weirs and some bridges, these revetments can fail during large floods, causing significant damage.

The 2004 levee project that raised the flooding level in Chiang Mai from +3.4 m to the current +3.7 m is a 6 kilometer long embankment protecting the city. It was however clear before the project was finished that it would exacerbate flooding elsewhere downstream. Recent studies suggest that this levee project should be carried for another 16 kilometers to reduce flood risk over the whole area.

Encroachment, along with unsuitable embankments is fought since the 2005 floods with the long term intention to bring the Ping river width back to its 1969 size when +4.2 m equivalent floods could pass through the city without significant flooding. Due mostly to administrative reluctance, attempts to control encroachment are rarely enforced.

All these methods can be assimilated as flood prevention. However, the RID and DDPM also have more active processes to manage water such as pumping flood water when conditions allow it or diverting water into other rivers and canals through sluice gates to reduce the impact of flooding in a specific area.

Figure 6. Flood conditions at some stage during the 2024 floods. Water was diverted and/or pumped into suitable canals by the RID and DDPM at that stage.

Administration of water management

As it is often the case in Thailand, coordination between agencies is difficult due to a top-down bureaucracy that limits any collaboration at a horizontal administrative level. Little concertation exists between water & irrigation management, disaster management, urban planning, locals, etc. Each institution also displays poor effectiveness due to poor design, absence of checks and balances, monitoring and evaluation, preventing appropriate responses; all characteristics seen in most Thai administrative bodies and described in the academic literature as institutional incapacities (see official actions against air pollution for similiar issues).

The 1952-1977 infrastructure development program was also associated with a set of policies and a legal framework that provided state control of water using physical infrastructure. The Royal Irrigation Department (RID) has now an overwhelming power in the management of waterways as they replaced the traditional muang-fai system with concrete structures. The RID became the main authority in water management and individuals, non-central governance and experts are reduced to an observing role.

The Hydrology and Water Management Center (HWMC) is the main administrative body for water level monitoring, flood situation and is the one who produce early flood warning. Following the 2005 floods, their role has been increased during floods to avoid some situations seen during that event where temporary protective dikes were erected or undone without proper oversight. They know work in collaboration with the RID and DDPM during floods to avoid such situations.

The Department of Disaster Prevention and Mitigation (DDPM) is mostly at work during and after floods. Its role is important during those disasters but their power is somewhat limited as policies which govern their actions are just vaguely related laws that have to be interpreted in the light of water management and floods. The DDPM also doesn’t have emergency funds of its own and all actions during floods requires the approval of higher administrative powers to assess funds and providing assistance to victims. Post-flood relief, repairs and evident upgrades that were supposed to occur after the 2005 floods took years (if done at all) to be applied and to some extent, it was still the case in the 2024 post-flood situation where allocated budgets did not cover some flood damage and relief in private but also public areas, and in some cases, recovery support was conditional, unproductive and inefficient, mostly due to administrative rigidity.

Structural mitigation and repairs are rarely undertaken by local authorities due to the lack of funds and is under the jurisdiction of provincial, federal and royal levels. The RID plays a role in the management of headwaters (in collaboration with the RFD), warning systems (in collaboration with HWMC), the structural base and main drainage of major roads (in collaboration with the ministry of transport) and minor roads and encroachment (in collaboration with local authorities). Ultimately, all of it falls under the jurisdiction of the RID to plan and deal with modification of water flow, dredging, retention ponds, reservoirs, diversion tunnels, new water gates, replacement and repairs of weirs, new river revetments and repairs and reducing/preventing river encroachment. Due to the administrative structure, the process to undertake these actions of recovery, repair and upgrades is slowed down considerably.

Figure 7. Evolution of the trends in water management between minimizing the impact of water shortage and floods (Y-axis) and water consumers (agricultural vs urban & industrial, X-axis)

Reaching a balance between stakeholders

The modernisation of the irrigation system in the 1980s gave important powers to the RID and impose upstream rules to most farmers with minimal notification, consultation or cooperation with local irrigation systems. As such, the RID is not always seen in a positive way by farming communities which have lost control over local water management and in a similar fashion to burning bans, they see it as a state intrusion into their traditional way of life (see public opinion on air pollution). It is estimated that the RID control in excess of 70% of the water inflow into irrigation system in the Chiang Mai basin.

The original projects were to provide agricultural water during drought but the extensive urbanization of the Chiang Mai basin and industrialization in Lamphun area has significantly modified water demands. Large dams were repurposed to produce electricity for the urban-industrial development, regulate monsoonal floods while reaching their limit as water storage for the dry season. Progressively, the same Bangkok-Central Plains attitude towards the Upper Ping has been transferred locally with a clear urban bias that sees waterways management mostly as a prevention for floods while agriculture has lost some priority in terms of water resources. Since the 1980s, the inequality coefficient towards availability of water resources has considerably widen between urban and rural population.

Since water management cannot be separated from the catchment management and particularly land use, other actors also play a role. A broad coalition of NGOs, the Royal Forestry Department, conservationists and ecologists sometimes frown upon anthropogenic water management through infrastructure. They are on occasion in opposition to the RID, rural people and non-urban politicians that wish a better control of waterways. A key issue is deforestation that is seen by some urban-conservationists as the reason for water shortages in the dry season and flooding in the rainy season. However, this opinion is not particularly supported by scientific evidence. There is a possibility that forests actually limit the amount of water infiltration during the dry season, and only have a limited effect on runoff during large rainfall event on a saturated soil. As it is the case with air pollution and forest burning (see air pollution), there is a tendency from the urban population and low land Thais to set the blame on non-Thai ethnic groups for their lack of “thainess” and what is seen as inappropriate methods and norms towards their rain-fed agriculture, Swidden-rotational systems and general forest management. It translates into vague threats to national security, biodiversity and in this case, water supply. The reality is that small scale irrigation systems likely have an insignificant impact downstream and actual farmland, albeit minimally increasing in some areas, decrease in others, with a change in the type of crops and intensification of agricultural practices that are not unique to hill tribes.