"We go to work when the sun rises, we rest when the sun sets. We dig wells and drink the water, we till the fields and eat the food-What is the Emperor's power to us!" (Book of Poetry, "Ground-Thumping Song") Since ancient times people have dug wells for drinking water and irrigation, but only in modern times have we come to a full understanding of groundwater with its broad extent and enormous volume.

It is calculated that about 97% of the water on the planet's surface is concentrated in the oceans. The ice sheets of both poles and the glaciers in the high mountains constitute about 2%. The 1% remaining represents the freshwater resources for mankind, and of this limited amount, 95% is underground.

Groundwater refers to water stored in subsurface aquifers, or permeable layers of rock, that has percolated, or "infiltrated," through the soil having originally fallen as rain or come from rivers, lakes and reservoirs. Because groundwater is not influenced by rainy or dry seasons, it can be used year round. Also, it maintains an even temperature and a stable quality. Unless polluted, it is mankind's best source of water.

Fishery officials from all over Taiwan have come to inspect this first-of-its-kind seawater station in Pingtung. But saline aquaculture has led to concerns about soil salinization, and debate continues. The round water tower in the picture is where seawater is stored after pumping.

Underground reservoirs

Alluvial plains and plateaus, criss-crossed by rivers, are highly permeable due to the accumulation of gravel, and a great deal of water infiltrates down through the soil. Thus these areas generally have plentiful groundwater. If the upper reaches of the rivers are verdant forests, the soil and vegetation will absorb great amounts of rain and will be able to support plentiful groundwater that acts as a natural "green reservoir."

Groundwater has been stored and utilized primarily on the eastern and western plains and plateaus in Taiwan. This includes the Tanshui, Lanyang, Choshui, Tsengwen, and Kaoping river systems. But because on the upper reaches of the Tanshui and the Tsengwen large reservoirs have been built that hinder the flow of the rivers, the flow downriver is drastically reduced, which affects the amount of groundwater recharge that occurs through infiltration. As a result only the three alluvial plains of the Lanyang, Choshui and Kaoping Rivers are areas that still contain plentiful groundwater.

The Pingtung Plain is an example. For thousands of years every branch of the Kaoping River, as well as the Linpien River, had its source in the Yushan and Central mountain ranges. From there gravel and mud washed downriver and piled up along the way, turning what had once been a large valley into a plain of more than 1,000 square kilometers. The length and breadth of this plain is covered with a fine network of rivers, which have created a super "underground reservoir."

"The smaller and lighter the stones, the further downstream has the action of the river transported them. The closer to the head of the alluvial fan where the river first discharges into the plain, the larger the stones," explains Professor Ting Cheh-shyh of National Pingtung University of Science and Technology's Department of Civil Engineering. The spaces between the large stones in this area are also comparatively large and it is easy for river water or rainwater to infiltrate the soil. After many long years this results in plentiful groundwater that slowly moves downriver through the aquifer.

Southern Taiwan has a six-month dry season, and people in the Pingtung Plain, where no artificial reservoirs have been built, must depend upon groundwater from summer rains infiltrating the soil for domestic, agricultural and aquaculture purposes. Prior to the 1980s an average yearly groundwater recharge of 1 billion tons was more than enough. Pingtung old timers recall: "Every family had its own artesian well. You didn't need tap water at all. You just stuck a bamboo pole in the ground and the water would come bubbling up."

Fig. 2: Land subsidence throughout Taiwan Note: Includes land formerly and currently subsiding. (source: Wang Chung-he, Academia Sinica / art by Tsai Chih-pen)

Aquaculture

In the 1970s the government made great efforts to expand aquaculture along the southwest coast. It encouraged farmers to reclaim land to raise shrimp, eels and clams, and fish farms quickly expanded. Because the deep groundwater was pure and had a constant year-round temperature, it was particularly suited to aquaculture, which is extremely temperature-sensitive. Using groundwater was also cheaper than using water from the public supply. The result was a series of deep wells along the coast, and what seemed like an unending supply of groundwater was continuously extracted.

"Over-pumping of groundwater by the aquaculture industry is only one cause of land subsidence," points out Professor Ting. If when water is being extracted downriver, there were recharging of the source further upstream, the situation wouldn't get so bad. But in the 1980s when the littoral Pingtung aquifer shrank and the ground was subsiding year by year, TaiSugar built a dike in and along the Linpien River bed in order to increase sugar cane acreage. In this way they gained more than 6,000 hectares of land. But they removed the original gravel of the river bottom and left only fine soil, greatly reducing the permeability. In addition, the more than 1,000-meter-wide river bed in which the Linpien had originally meandered was now reduced to a channel of 200 to 300 meters in which the river was constricted, increasing its speed toward the ocean and eliminating the opportunity for the water to infiltrate down into the aquifer.

"Beginning in the 1980s the groundwater level in the Pingtung Plain continually sank and today it is below sea level," says Wang Chung-ho, an Institute of Earth Sciences research fellow at Academia Sinica. At the present time seawater has intruded into the aquifer of the Pingtung Plain as far as nine kilometers inland. An area of more than 100 square kilometers has been affected. Already more than 30 billion tons of groundwater have been permanently lost through salinization.

The tortuous story of the groundwater of the Pingtung Plain going from plentiful to scarce is a microcosm of the mismanagement and over-extraction of groundwater throughout Taiwan. Water Resources Agency statistics show that in the past more than 20 years the area of land subsidence has reached 2,600 square kilometers, amounting to one quarter of the area of all plains in Taiwan. Of this total, land subsidence in Yunlin is almost 880 square kilometers, the most seriously damaged area of all, while Chiatung Township in Pingtung County has suffered the deepest subsidence at more than three meters, equal to the height of a single-story building.

As the development of additional surface water resources gets more difficult, underground water is gradually receiving more recognition. But different from the days of our ancestors when one could just dig a well and drink the water, today we need more scientific ways of developing and managing water resources.

Beyond recovery

There are many causes of land subsidence. In Taiwan it results primarily from the long term, heavy and concentrated over-pumping of groundwater. If over-pumping stops, can the ground strata return to their original condition?

"Unfortunately, the answer is no," explains Professor Lee Cheng-haw of National Cheng Kung University's Department of Resources Engineering. This is because the collapsed strata are mostly "aquicludes," i.e., relatively impermeable rock strata. If you can imagine the structure of the strata as a kind of multi-layer cake, then the top layer is the aquifer, followed by the aquiclude, then another aquifer and so on for about five to seven layers, one alternating with the other. (See fig. 3). The spaces between soil particles within the aquifers are large and thus the stratum has a high degree of permeability. The aquicludes are composed of mudstone with small spaces between particles and they have poor permeability. When large amounts of water are extracted without timely replenishment, this can press the soil particles tightly together. The soil loses its ability to support the stratum above it and collapses or subsides. Once the spaces separating the soil particles are compressed, it is very difficult for them to expand again. At the same time, space available to store water in the aquifer is reduced.

Because land subsidence in Taiwan takes place on the coast, when the groundwater table is lower than sea level, ocean water can intrude, making what groundwater remains salty and unusable, further destroying precious water resources.

Soil salinization can also erode the steel bars in reinforced concrete, destroying the structure of bridges and buildings, considerably shortening their lifespan. We know that many dikes and pavements have been cracking apart over the years and that local government officials are at a loss as to what to do and just shake their heads in the face of huge repair costs.

Following land subsidence, the drainage system is as good as non-existent because of the new low-lying topography that results. When it rains, the place becomes a "water world," putting the people's life and property at risk and lowering their quality of life. And it has become a long-term problem and concern for the government.

To reduce the volume of water used by water-consuming industries the government in recent years has been making great efforts to steer aquaculture toward new models of production, such as employing a brackish/freshwater mixture as well using recycled water.

Ten years of prevention

In view of the disasters brought on by land subsidence along the coast over the last 20 years, the government has promoted a series of preventative measures that include the announcement of groundwater control regulations, designating groundwater control zones, prohibiting wells that don't meet regulations and implementing land-use controls. In the last ten years it has promoted two stages of an Action Plan for Land Subsidence Prevention. The first ran from 1995 to 2000 and the second runs from 2001 to 2008. It has also organized a Land Subsidence Prevention Service Team to go into local areas and deliver public service information.

"The main principle of subsidence prevention is to reduce the extraction of ground water and increase the use of surface water," says an official with the Water Resources Agency's Hydrology Division. The emphasis includes reducing the number of industrial consumers of water, encouraging agriculture to engage in fallowing and forest plantations, guiding aquaculture to move toward saltwater or brackish water aquaculture and to get increased control of groundwater and promote the use of "public wells."

Professor Lee Cheng-haw points out that after ten years of prevention the public's awareness and understanding has been raised considerably. Previously when researchers went out to inspect wells the fish farmers would set their dogs on them. Because people in recent years have come to understand the dangers of land subsidence, in addition to water conservancy, the concept of water recycling has been increasingly accepted. Currently there has been quite a bit of success with recycled water in the raising of porgies and eels.

"The creation of the national groundwater monitoring network only happened within the past ten years," says Lee Cheng-haw. Because the cost of a monitoring well is high, they were not set up in the past, so there was no way to get a handle on changes in groundwater level, not to mention manage it. It hasn't been until recent years when the government has spent billions to build almost 300 monitoring wells on all of Taiwan's plains that there has been transparency in information on groundwater hydrology. But a corresponding management system, for example, a mechanism for officially announcing when water levels are safe, when they merit a warning and when there is a serious drop in water levels, as well as setting up measures to respond to these things-all this waits to be worked on.

According to Water Resources Agency statistics, over the past ten years the amount of groundwater extracted dropped to 5.6 billion tons in 2004 from 7.1 billion tons in 1994. The area of continuing land subsidence has been gradually on the decline as well. The director-general of the agency, Chen Shen-hsien, points out that subsidence prevention is a long-term battle and results cannot be immediate. For areas where subsidence has slowed, long-term efforts at promoting preventative measures are still necessary. But in the Yunlin and Changhua area, worst hit by subsidence, the central government will create an inter-ministerial committee to promote a subsidence prevention pilot zone, and has already budgeted NT$15 billion that will include funds for moving some 70 irrigation association and Taiwan Water Corporation deep water wells beyond the high-speed rail line zone, and for closing down permanently some 40 wells. In addition the government will promote the construction of the Hushan Reservoir on the plain of Yunlin to increase the supply of surface water.

Fig. 2: Land subsidence throughout Taiwan Note: Includes land formerly and currently subsiding. (source: Wang Chung-he, Academia Sinica / art by Tsai Chih-pen)

"The more things change..."

Although there has been some success in prevention, in view of the speed with which the environment is deteriorating, many experts are still worried. "Taiwan is already losing its soil inch by inch, and the real crux of the problem, over-use of groundwater, has not been solved," notes Wang Chung-ho.

The most obvious thing is that illegal wells are still quite common.

"Although illegal wells can be filled and sealed up according to the law, if there is no water source to replace them, suddenly sealing them will certainly endanger people's livelihood." This is openly admitted in the Water Resources Agency's "Land Subsidence Prevention Report." Because every well sealing leads to opposition, the police have to be brought in. There are many obstacles. Also, local councils will often just cut budgets for water-related items. As a result, local governments are not very willing to enforce the law in these instances.

Industrial policy is also a key point, say many experts with frustration. In recent years environmental awareness has dawned in north and central Taiwan and one industrial park after another has moved south. Because industries don't have much room for compromise on their use of water, and once started the supply must be guaranteed, this increases the pressure on groundwater usage. And often the government decides first on the industrial park location and only then makes preparations for water resources, thus making the management of water resources even more difficult.

The chairman of the Changhua Aquaculture Association, Lin Chi-min, is upset. He points out that the fish farmers of the association use groundwater in accordance with the law, and in recent years most have switched over to recycled water, while the real big users are the large factories. Tucked away behind private factory gates, pumps are going 24 hours a day and it is difficult for outsiders to know what's going on, yet there is precious little criticism.

Wang Chung-ho says that currently Taiwan uses a yearly average of 5.5 billion tons of groundwater, with 90% being used in the southern and central parts of the country. Rainfall in the south has always been very uneven; add to this the change in global climate patterns, and rain during the dry season in the future is likely to steadily diminish and increase dependence on groundwater. Obviously after 20 years of over-use, the imbalance between surface water and groundwater is getting worse, and Wang issues a serious appeal. Unless the situation is improved, not only will agricultural and industrial development in central and southern Taiwan be hampered by lack of water resources, further, if you want to transfer water from north to south, or from east to west, this will certainly affect development in the northern and eastern part of the country.

Long-term, high-volume, concentrated over-pumping of groundwater has been difficult to deal with, even for the Pingtung Plain where groundwater is plentiful. In coastal Chiatung Township, situated along the coast, land subsidence is severe. The picture shows a home sunken a story deep into a fish pond.

"First aid"

Wang Chung-ho believes the most pressing thing at the moment is to replenish the water that has been over-pumped. At every alluvial fan head, where a river enters the plain, a deep well should be sunk to directly recharge the aquifer and bring the water level back up, to prevent further subsidence. "The Choshui alluvial fan and the Pingtung Plain both have good natural attributes. If the aquifers are recharged quickly, they can be saved."

In addition, the usage rate of surface water must be rapidly increased. Wang Chung-ho cites the Tsengwen Reservoir as an example. "With a capacity of 600 million tons, there should be a yearly recycling of from two to three times that," but in fact the amount is only one to two times the capacity. In the past two years only 300 to 400 million tons were drawn off. To have reservoirs and not make good use of them is really a shame. Wang thinks the Water Resources Agency's approach in recent years of feeding the Tsengwen Reservoir from the Laonung weir is a good one. It can raise the usage of surface water and reduce the burden on groundwater.

How to effectively combine the use of groundwater and surface water has been a trend in water resource management in recent years. Nevertheless, today with surface water resources becoming ever scarcer, the experts are putting more thought behind the best use of "underground reservoirs."

In recent years large-scale industrial parks have been setting up in southern Taiwan, greatly increasing pressure on the water supply for an area already with an unstable supply. Many experts regretfully point out that industrial policy is actually another culprit causing groundwater over-pumping.

We have plenty of groundwater!

Lee Cheng-haw points out that if groundwater could be effectively managed we could break out of the mindset that groundwater should only play a "supplementary" role as an "emergency reserve." We could even regard it as our primary water source and so manage and control it from that perspective. He avers, "Taiwan has plenty of groundwater!"

The main principle behind effective management is dispersal: temporal (amount of time the water is pumped), geographic (where it is pumped) and geologic (from what strata is it pumped), plus corresponding control over replenishment and "water levels." Lee Cheng-haw explains Taiwan's current problem is that location, extraction time, as well as the aquifer stratum from which the water comes, are all concentrated so that the ground is being "pumped to death."

As for aquaculture, not only is it concentrated along the coast, the water is extracted during the day, and when the weather is cold it is pumped non-stop to maintain the water temperature of the fish ponds. Also, because the deep-stratum aquifers have the best water, all the wells are sunk down to two or three hundred meters.

Moreover, the Taiwan Water Corporation, the irrigation associations and other legal heavy users of water are also concentrated along the coast and use aquifers more than 200 meters deep. They should all be included in an overall plan.

Lee Cheng-haw, citing a hundred years of proven experience in Europe, points out that in thinking about groundwater the notion of controlling "water levels" should replace the current idea of managing "water volume." because even if the water volume of an area is considered adequate, an over-concentration of pumping will still create problems like land subsidence.

Aside from effective management, Professor Ting Cheh-shyh says that Taiwan should put more effort into diverting the plentiful rainfall of the rainy season into broad "underground reservoirs." He estimates that in July 2004 during the flooding from Typhoon Mindulle, in less than one week the topmost aquifer of the Pingtung Plain saw an increase of more than 600 million tons of groundwater. And this water had infiltrated through a natural gravel filter making the quality far superior to that of the surface water.

Professor Ting Cheh-shyh of National Pingtung University of Science and Technology is calling for Taiwan to break out of its passive mindset with regard to groundwater, which focuses on the "prevention of over-pumping," and actively utilize the abundant water of the rainy season to fill huge underground reservoirs. The picture shows Professor Ting at Wanlung Farm, a target area for groundwater recharge plans.

Using underground reservoirs

Ting has long studied the three elements behind the "artificial recharging" of groundwater: hydrogeology, water resources and technology. He considers it quite possible for Taiwan to artificially recharge aquifers at alluvial fan heads. The Choshui River and the Pingtung Plain both have many suitable locations. Currently, Ting is directing the Wanlung Farm/Linpien River groundwater recharging project. A 300-hectare artificial lake area is planned that will be fed by the Linpien River when river water is plentiful. The water from this area will infiltrate and recharge the underground aquifer. The plan was approved by an environmental impact assessment and will go into operation very shortly.

With regard to the problems of river water turbidity and the silting up and blockage of water purification plants caused by heavy rainfall, Ting Cheh-shyh suggests making good use of groundwater's "natural water purifier." "We should not use river water directly; we should change our strategy," he says. The government could set up pumping wells alongside rivers. When river water is plentiful, groundwater could be extracted. When extraction occurs the river water would quickly infiltrate and recharge the aquifers. This would also have the effect of reducing floodwaters. And when the surface water becomes polluted or when the turbidity is too high to handle, groundwater can still be extracted and used as normal. If water levels can be monitored in coordination with this approach, then we can avoid major water shortage predicaments like what occurred last year in southern Taoyuan.

"While surface water resources are diminishing daily, groundwater resources, which are ten times that of river and lake water, are becoming more important." More than ten years ago experts were already issuing public appeals but the old notion that groundwater extraction inevitably causes subsidence blocked the development of groundwater research in Taiwan. Because there was a lack of experts in this area, surface water remained the focus of thinking about water resources.

In recent years, the topic of groundwater has been gaining attention. Will the water buried under the ground be able to bring a ray of hope to Taiwan's difficult water resource problem? Perhaps the answer is to think beyond "prevention."