Agricultural Water Conservation and Sustainable Water Resource Utilization in Northwest China

Author: Chief Editor: Kang Shaozhong
Publisher:
Publishing Date: 1999-04-01
Features: The book is divided into nine chapters, including General Introduction, Mechanism of Agricultural Water Conservation, Crop Water Requirement and Water-Saving Irrigation System, Soil and Crop Water Monitoring and Forecasting Technology, Farmland Water-Saving Irrigation Technology, Water Transport System Water-Saving Technology, Water Distribution and Flow Regulation Technology in Irrigation Districts, Efficient Utilization Technology of Rainwater and Turbid Water Resources in the Loess Plateau, and Sustainable and Efficient Utilization Technology of Surface and Underground Water Resources in the Northwest. The book is systematic, comprehensive, rich in data, and combines theory with practice, highlighting the research achievements of the Institute of Agricultural Water Conservancy and Engineering at Northwest Agricultural University. It is suitable for scientific and technical personnel in farmland water conservancy, soil physics, agricultural meteorology, plant water physiology, farmland ecology, agricultural hydrology and water resources, agricultural water conservancy and engineering, water-saving agriculture, water environment, and soil and water conservation. It can also serve as a teaching reference for postgraduate and undergraduate students in relevant fields. Excerpt: Chapter General Introduction Section Water Supply and Demand Situation in the Northwest and Requirements for Developing Water-Saving Agriculture
1. The Role of Water-Saving Agriculture in the Sustainable Development of China's National Economy
Water scarcity has become a global issue. China's total water resources amount to 2.8 trillion m3, ranking sixth in the world. However, per capita annual water resources are only 2,200 m3, less than one-fourth of the world average, ranking 109th globally, placing China among the 13 most water-scarce countries. The average water volume per hectare of arable land is 28,050 m3, only four-fifths of the world average. Moreover, China's water resources are unevenly distributed geographically. 81% of the country's water resources are concentrated in the Yangtze River Basin and its southern regions. The northern Yangtze River region accounts for 45.3% of the national population and 64.1% of the arable land, but only 19% of the country's water resources, with a per capita water volume of 517 m3, equivalent to one-fifth of the national average and one-twentieth of the world average. Therefore, water resource issues are more prominent in northern China. The Food and Agriculture Organization of the United Nations has recently highlighted the severity of water scarcity in northern China, southern India, and parts of Mexico. Due to water scarcity, 70 million people and 60 million livestock face drinking water difficulties. More than 600 cities are water-scarce, with over 300 suffering from severe water shortages, including more than 110 cities with critical water scarcity. Water scarcity has also led to excessive extraction of surface water and over-exploitation of groundwater, resulting in frequent river drying and groundwater level declines, causing serious ecological and environmental problems. Since the 1980s, global warming has become more pronounced, exacerbating droughts in northern China. Among China's natural disasters, droughts have the greatest impact on agricultural output. Since the 1990s, the annual area affected by droughts has been around 2.7 million hectares, more than 1.5 times the 1950s level, with disaster-stricken areas increasing threefold. In 1994, the national drought-affected area was 3 million hectares, with disaster-stricken areas reaching 1.73 million hectares, resulting in a 26 billion kg reduction in grain output. In the future, with the development of industrial, agricultural, and urban economies, the contradiction between water supply and demand will further intensify. In addition to expanding water sources, water conservation should be the primary approach to addressing current water scarcity. Agriculture is the largest consumer of water, primarily used for irrigation. China currently has 5 million hectares of irrigated land, the highest in the world, accounting for about half of the country's arable land. The annual water consumption for agricultural irrigation is approximately 400 billion m3, accounting for 80% of the total water usage. However, the effective utilization rate of agricultural water is very low, with only 30%–40% in canal irrigation areas and about 60% in well irrigation areas. In contrast, some developed countries achieve over 80%. On the other hand, China's irrigation water use efficiency is also very low, with less than 1 kg of grain produced per cubic meter of water, while Israel produces 2.32 kg per cubic meter, and some developed countries produce over 2 kg per cubic meter. This indicates that we are far from achieving water conservation and scientific water use. Therefore, developing water-saving agriculture is imperative. It is a fundamental measure to alleviate China's water scarcity, promote sustainable water use, and ensure the sustainable development of agriculture.
2. Water Supply and Demand Situation in the Northwest and Urgency for Developing Water-Saving Agriculture
(1) The main natural characteristics of the Northwest are arid and rainy conditions, severe soil erosion, and fragile ecological environments, but there is great potential for agricultural development. The arid and semi-arid regions of the Northwest include Shaanxi, Gansu, Ningxia, Qinghai, Xinjiang, and the southwestern part of Inner Mongolia, covering a total area of over 4 million square kilometers, accounting for about 42% of the country's total area and 8% of the national population. The currently cultivated land is 13.333 million hectares, with potential for further development of 2.6667 million to 3.3333 million hectares, ranking first in per capita cultivated land in China. The Northwest is rich in coal, oil, natural gas, and mineral resources. The region has a long history of agricultural development, with the Chinese nation settling in fertile areas along the Yellow River, such as the Wei River Valley, as early as 6,000 years ago. During the Western Zhou and Spring and Autumn Warring States periods, the Yellow River region became the agricultural center of the country. In 121 BC, Huo Qubing established military posts in the Hexi Corridor, promoting agricultural development, with irrigation agriculture flourishing in the middle and upper reaches of all rivers. The irrigation agriculture in the lower reaches of the Hei River was renowned, earning it the names "Golden Zhangye" and "Silver Wuwei." Since the founding of the People's Republic of China, the development of agriculture has been significantly advanced through the construction of water storage, water diversion, and water lifting irrigation projects, as well as the control of soil erosion and the improvement of alkaline land. The Guanzhong Plain, Hexi Corridor, Xinjiang inland river region, Qinghai Huangshui Basin, and Qaidam Basin, as well as many high-lift water lifting irrigation areas along the Yellow River, have become important grain and cotton production areas in China. However, due to the region's natural conditions and long-term adverse effects of human activities, vegetation has been destroyed, productivity has declined, ecosystems have, and natural disasters have become frequent. Currently, this region is the most ecologically fragile in the country and one of the areas with the highest concentration of impoverished populations. The main natural characteristics of the region are low precipitation, aridity, insufficient water resources, severe soil erosion, and fragile ecological environments. Most areas of the region receive less than 400 mm of precipitation annually, with 2 million square kilometers receiving less than 200 mm, and eastern Xinjiang, western Hexi, and central-western Qaidam receiving less than 50 mm, while deserts and Gobi areas receive less than 20 mm. Evaporation exceeds 1,000 mm. The severe soil erosion in the Loess Plateau of the Northwest has not only deteriorated the ecological environment within the region but has also led to large amounts of sediment entering the Yellow River, making it one of the world's most sediment-laden rivers. Statistics show that the average annual sediment discharge of the Yellow River is 1.6 billion tons, with about one-fourth deposited in the lower reaches. The middle reaches of the Yellow River, including northern Shaanxi, eastern Gansu, and Dingxi, suffer the most severe soil erosion, with river floodwater sediment concentrations as high as 900 kg/m3 and soil erosion modulus reaching 6,000–10,000 t/km2. In some severely eroded areas, it exceeds 20,000 t/km2. During the dry springs in southern Xinjiang, western Hexi, and Ningxia, strong winds often form sandstorms, with sand and stones flying,, and sand dunes moving, burying farmland and swallowing oases. This has had a serious adverse impact on agricultural and pastoral production and ecological environment maintenance. Water scarcity is the most important constraint factor for the development of industrial, agricultural, and ecological balance in the Northwest. The five provinces (autonomous regions) of the Northwest account for one-third of the country's area but only 223 billion m3 of water resources, representing only one-twelfth of the national total. For example, the Loess Plateau (including the Hetao region) covers 6.9% of the country's land area, with 12.2% of the arable land, but only 1.8% of the water resources, with 3,720 m3 of water per hectare of cultivated land and 654 m3 per capita. The per unit cultivated land area and per capita water volume are only 14% and 24.1% of the national averages, respectively. The inland region of the Northwest covers 25.8% of the country's land area and 3.9% of the arable land, with 4.0% of the national water resources. Water scarcity is even more severe in some local areas. For instance, the total water resources in the Hexi Shiyang River Basin are 1.728 billion m3, while the total water consumption in the region is 2.0142 billion m3, accounting for 116.6% of the available water resources, with severe over-exploitation of groundwater. However, the Northwest is rich in sunlight and has a large diurnal temperature range, making it suitable for the production of grain, cotton, and some special crops. There is great potential for agricultural development.