In 1988, the Gansu Research Institute for Water Conservancy (GRIWAC) began a project designed to research, demonstrate and promote rainwater harvesting (RWH) in the Gansu Province of China. The project was so successful that by the end of 1994, about 40,000 rural households had built their own RWH systems and by the end of 2001, there were 2.2 million newly built storage tanks using GRIWAC’s methods. By 2001 these new techniques had made the irrigation of 236,000 ha of land possible while at the same time, those benefiting from this domestic water project had increased to nearly two million people. Thanks to this project crop yields have increased by roughly 40 percent in an average year and even more in a dry year.

Background
The semi-arid Gansu Province is one of the poorest and driest areas in China. Droughts and dry spells are common in this mountainous area where people depend primarily on rain-fed subsistence agriculture. It was therefore clear that a simple and affordable rainwater harvesting system combined with an integrated approach to improving agricultural production would significantly improve the lives of local Gansu farmers.

In the mountainous Gansu Province over 90 percent of the population live in the rural areas. In this area of primarily subsistence agriculture, most farmers have traditionally relied on unfavorably distributed seasonal rainfall. Two-thirds of the rain falls between July and September each year, often in the form of heavy thunderstorms. Only about 20 percent of the rain falls in the spring, when crops need water most and it is only possible to grow one crop per year.

The main crops grown in Gansu are wheat and maize. In central Gansu, spring wheat is the most common crop, but recently maize grown with plastic mulching has been widely adopted due to its higher yield and its adaptability to natural rainfall. This crop is sown in late April and harvested in late September. Plastic mulch is essential for growing maize in the area because it raises the temperature of the soil, which allows the crop to mature. In eastern Gansu, winter wheat and maize are the most common crops. In the most mountainous areas, cows and horses are used for sowing, ploughing and tillage while harvesting is done mainly by hand.

Water scarcity
Water resources in the area are scarce. Most of the river runoff is salty and cannot be used for drinking or irrigation. Groundwater is also limited and is poor quality. Because of the mountainous topography and geological condition it is both difficult and expensive to divert water from other watersheds, making drought more frequent. Studies in Gansu show that heavy droughts, reducing yields by more than 30 percent, have occurred in 11 of the past 40 years.

Under these adverse conditions, yields are as low as 1000 kg/ha in a normal year. In dry years, yields do not even cover the cost of seed. Without irrigation, it is impossible to grow most cash crops. As a result, the annual family income from a little less than one hectare of land is between US$500-US$750. The poor productivity of land has forced farmers to reclaim as much ground as possible even on steep slopes. This has caused more soil erosion and land degradation and this in turn has had a negative effect on agricultural productivity. As a consequence the environment has deteriorated rapidly, and an inadequate drinking water supply, food insecurity, low income and serious soil erosion have become common features in the area.

The RWH solution
The RWH system consists of a rainwater collection field and tanks for water storage, water supply and irrigation facilities. Less permeable surfaces of existing structures are used for rainwater collection. In the RWH system for domestic water use, tiled roofs and concrete lined courtyards are commonly used to produce cleaner water. Paved highways, country roads, threshing yards and sport grounds are used for collecting rainwater for irrigation purposes. Sometimes, hilltops or slopes are lined with concrete slabs to increase runoff.

Traditional underground tanks, known locally as Shuijiao and Shuiyao, are the most common types of water storage. The total investment for each Shuijiao is about US$120, of which US$50 is subsidised by the government. Farmers in the form of labour, local materials and some cash supply the remaining investment.

The tanks usually have a bottle shape with a diameter of about 3-4 m and a depth of 5-6 m. Irrigation tanks generally have a capacity of 30-50 m3. A concrete, dome-shaped top with a thickness of 10-12 cm helps to sustain the soil weight and the load on the surface. The bottom of the tank is made of 10 cm thick concrete and a hole in the centre acts as both a water outlet and a manhole.

An underground tank has the advantage of preventing evaporation loss and maintaining a low temperature, which helps to maintain water quality. Each tank is used for the supplementary irrigation of one Chinese mu (approximately 670 m2). One structure will generate two water applications of approximately 20mm each, enough to mitigate one dry spell during the growing season. A hand pump usually supplies water for domestic use.

The limited amount of rainwater available for irrigation is applied sparingly to crops, using the principle of limited irrigation. This means that water is applied in limited amounts during a few critical periods of crop growth. For this purpose, experiments have been conducted that determine the best time to provide different crops in the area with supplemental irrigation. The most commonly used methods are very simple, affordable and effective. For example, irrigation when the seeds are being planted or supplying water through the holes in the plastic sheeting. If farmers can get support or a loan, they also use drip irrigation and mini-sprinkling for high value crops.

Extending the project
Experiences over past decades show that water is a key factor in the struggle to change basic conditions in the area. RWH has been shown to be the most effective way for local people to access water. People in the area have a long tradition of harvesting rainwater for domestic water use, but the quantity of water collected was far from sufficient to meet domestic demand, let alone the water needs of crops.

The Gansu Research Institute’s aim was to improve the efficiency of rainwater utilisation and work out RWH technologies that were most suited to local conditions. The Project was very successful in supplying water both for household and crop use.

In 1995, a once-in-sixty-year drought occurred. Millions of people suffered from thirst and almost all the summer wheat died. Because of the successful experiences of the GRIWAC RWH project, the local government decided to initiate a “1-2-1” rainwater harvesting project, aiming to solve the drinking water problem for one million people in the area. In this project, government and donors supported each household with cement equivalent to US$50 to enable them to build one collection field, two underground tanks and to irrigate one piece of land with rainwater to develop the courtyard economy enabling them, for example, to plant vegetables or fruit trees in the courtyard, raise animals and poultry and process agricultural raw materials. By the end of 1996, there were 1.2 million beneficiaries of this project.

In 1996, a follow-up RWH Irrigation Project was initiated, starting with pilot projects at 12 sites with different natural and social conditions. The project was later extended to a much larger area. By the end of 2001 there were 2.2 million new tanks making the irrigation of 236,000 ha of land possible. By this time, those benefiting from the domestic water project had gone up to nearly two million.

Benefits
The 15-year experiences of RWH in Gansu have proved that RWH can provide safe and cheap water for domestic use and increase production by providing supplemental irrigation to crops. Crop yields have increased by around 40 percent in a normal year and by much more in a dry year.

With water in their tanks, farmers can diversify their cropping systems. Before the project, the only foods available at the family table were potato, onion and cabbage. Now, other crops that are sensitive to water stress can be grown, like cucumber, tomato, eggplant, pepper, tobacco, and herbs. Simple greenhouses have also been developed to grow vegetables and flowers. Water collected from the roofs of greenhouses can meet 40 percent of the water needed to have three harvests of vegetables. The remaining 60 percent of water needs to come from other catchments. The simplified green-house built with bamboo and steel rods and covered with plastic films costs about US$1000, while the annual net profit can be up to US$350-US$500. At this rate, investment can be recovered in 2 to 3 years.

When land productivity improved, farmers started to participate more in the Land Conversion Programme initiated by the State Government. This programme encourages farmers to plant less fertile land with trees and grassland species to improve the ecosystem. Irrigation with rainwater is a precondition for the establishment of new vegetation.

Drought-proofing villages
Luoma Village is located in the northern part of Huining County, which is one of the 592 key impoverished counties in China (the annual rainfall is only 250 mm). The village has a population of 323 living in 65 households. Before the RWH project, the annual food production per capita was less than 300 kg, annual income per capita was less than US$50 and local people had no water supply for domestic use.

Luoma was chosen as one of the pilot RWH projects in Gansu Province. From 1996 to 1998, the village built 330 Shuijiaos, 130 for the domestic use, 65 for the courtyard economy and the remaining 195 for field irrigation. During the recurring droughts between 1999 and 2000, the RWH system not only ensured water for domestic use and animal husbandry, but also provided enough water for the supplemental irrigation of 22 hectares of land.

Now that they have water, farmers have changed their cropping system by planting maize instead of summer wheat. Maize requires more water and heat in order to mature properly, but produce much higher yields than wheat in the region because of its longer growing period and superior adaptability to natural rainfall patterns. Annual yields have now increased from 975 kg/ha of wheat to 3950 kg/ha of maize. Annual food production has increased by 144 percent and income per capita has increased by 187 percent. Even in years of severe drought, households have enough to meet their food needs.

Experiences
The phenomenal success of the RWH project in Gansu is the result of wide participation of the farmers and firm support of the government. The main experiences of the project in Gansu can be summarised as follows:

• Household ownership of RWH system is the key factor to the high degree of motivation shown by farmers. Unlike the key water projects owned by the State or big enterprises, which farmers regard as “welfare”, most the RWH systems belong to the households themselves.
• Both farmers and government can afford the inputs for the RWH system. The high profits gained from RWH means that investment can be recovered quickly.
• RWH is a tradition of the local people, but it has been updated with appropriate modern technology. This meant that farmers were more ready to accept it.
• With a little assistance from villager technicians, farmers can build their own RWH system. This decentralised approach of the RWH project suits the natural and social conditions of this mountainous and impoverished area.
• Proper preparation, organisation and management of project implementation are also important success factors.