Implementing the water-saving priority policy and building a water-saving society is the fundamental solution to China's water scarcity. Vigorously developing and promoting water-saving technologies and products, and achieving efficient water conservation through science and technology, are key links and major tasks in building a water-saving society. In recent years, relevant national departments have issued a series of policies and regulations to encourage and support the development and promotion of water-saving technologies. Water-saving technologies in China have developed rapidly, with many advanced and applicable water-saving technology products emerging in fields such as industry, agriculture, and services. Through innovative promotion and application models, these technologies have been widely applied, achieving good water-saving results. In response to the water use demands in China's key sectors and the development status of water-saving technologies, and considering some emerging water-saving technologies and models, relevant opinions and suggestions are proposed for carrying out water-saving technology R&D and promotion work, and comprehensively improving the level of water conservation.

 I. Agricultural Sector

Agricultural water use accounts for 62% of China's total water consumption. Building a water-saving society requires a focus on agricultural water conservation. In recent years, to complete the rehabilitation, upgrading, and modernization of irrigation districts, China has promoted efficient water-saving irrigation on a large scale. Advanced technologies such as sprinkler irrigation, micro-irrigation, drip irrigation, pipe irrigation, rainwater harvesting and supplemental irrigation, soil moisture monitoring, and water metering have been widely applied in farmland water conservancy construction projects. The effective utilization coefficient of farmland irrigation has reached 0.52, achieving significant water-saving results. Subsequently, in addition to updating, improving, supporting, and systematizing existing agricultural water-saving technologies, it is necessary to focus on strengthening research and promotion in the following aspects.

1. Pipeline-based Irrigation Water Delivery

Most agricultural irrigation in China uses canal systems for water delivery, which results in significant water losses through evaporation and seepage. According to surveys, in northwest China, water conveyance projects using canals without anti-seepage measures lose nearly 50% of water from the source to the field due to evaporation and seepage. The next step involves organizing applied research on pipeline-based water delivery in irrigation districts, in conjunction with the construction of modern water-saving irrigation districts. In particular, the economic feasibility, reliability, and applicability of new technologies and products such as new-type bamboo-wound composite pipes and PVC-O (oriented polyvinyl chloride) pipes should be evaluated. By integrating modern Internet of Things (IoT) technology, flow measurement and metering technology, pipeline gate control technology, and pipeline sediment cleaning technology, comprehensive solutions for replacing canals with pipes should be proposed.

2. Subsurface Irrigation Technology

Subsurface irrigation technology is a method that uses emitters buried in the field's plow layer to moisten the soil near the crop root zone from below through capillary action. In the past, limitations in material technology hindered the application of subsurface irrigation. In recent years, with the development of membrane material technology, the bottleneck of subsurface irrigation technology is expected to be broken. Efforts should be increased to support technologies such as micro-moisture tubular semi-permeable membrane irrigation, trace irrigation, and PE tempered microporous membrane technology. The scale of application demonstration projects should be expanded to make the technologies more mature, establish design standards and complete application solutions, laying the foundation for large-scale promotion and application.

3. Sponge Farmland Technology

Precipitation in China is highly uneven in terms of time and space. How to make full use of rainwater resources for agricultural cultivation warrants in-depth study. Drawing on the concept of sponge city construction, efforts should be organized to develop new materials, technologies, and processes for rainwater utilization, and to establish and improve the sponge farmland technology system. Special emphasis should be placed on basic research on organic polymer water-control materials, plant nutrient elements, microbial activators, and soil compaction improvement factors. Materials should be developed that have good water absorption and retention effects, release water evenly and slowly, and possess functions such as water saving, fertilizer retention, efficiency enhancement, soil loosening, and stress resistance. Farmland should be transformed into sponge farmland with strong water absorption, retention, and drought resistance capabilities. Based on existing technology applications, an average annual investment of over 100 yuan per mu can achieve a relative water-saving rate of 40% and significant yield increase effects. Efforts should be organized to explore how to form complementary advantages with other water-saving irrigation technologies in water-scarce areas of northwest China; how to leverage the role of water-saving and extraction reduction projects in north China; how to combine with rainwater harvesting and supplemental irrigation to achieve water saving and yield increase in rainy southern regions; and how to achieve plant water retention, water saving, yield increase, and efficiency enhancement in rocky desertification control in southwest China.

4. Water-Saving Facility Agriculture

The high-efficiency plant factory production model can save water, energy, and fertilizer, effectively improving the yield and quality of agricultural products. It represents the development direction of modern facility agriculture. A mechanism for multi-department joint research and collaborative innovation should be established to jointly tackle key technologies such as energy-saving and thermal insulation materials for facility agriculture greenhouses, plant lighting semiconductor light-emitting technology, and water-saving irrigation, forming a plant factory technology system suitable for China's needs. High-pressure fine water mist root irrigation technology atomizes nutrient solution into micron-sized droplets and directly sprays them as mist onto plant roots suspended in the air, providing the water and nutrients needed for plant growth. Compared with conventional greenhouse cultivation, the water-saving rate exceeds 85%, and vegetable yield is 5 to 10 times that of conventional greenhouses. If integrated with energy-saving insulation, artificial supplementary lighting, and other technologies to form standardized products, it will provide technical support for water saving in facility agriculture.

II. Industrial Sector

Industrial water use accounts for 21% of China's total water consumption. Major water users include high water-consuming industries such as thermal power generation, steel, coal, mining and mineral processing, textiles, petrochemicals, food, and fermentation. Developing and promoting industrial water-saving technology products holds enormous potential and broad prospects.

1. Zero-Discharge and Waste-Free Technology for Industrial Cooling Water

Industrial cooling water accounts for over 60% of industrial water use. It is necessary to conduct research focused on upgrading cooling water treatment technology to achieve zero wastewater discharge. To avoid corrosion caused by microorganisms and scaling due to water hardness, and to improve water conveyance and heat exchange efficiency, the traditional practice involves adding various water treatment chemicals to industrial cooling water networks. When the chemical content in the water reaches a certain level, the water must be discharged and replaced with fresh water, which wastes water and causes pollution. In the field of industrial cooling water treatment, the use of DTRO flat-sheet membrane filtration technology, high-voltage electrostatic treatment technology, strong electromagnetic field water treatment technology, and electrolytic water treatment technology has significantly reduced the use of chemical agents and sewage discharge, achieving certain water-saving, energy-saving, and pollution reduction effects. In the future, emphasis should be placed on in-depth research and vigorous promotion of comprehensive ion membrane electrolysis circulating water treatment technology. This technology combines micro-electrolysis descaling technology, ion-based algae and bacteria killing technology, and electrochemical derusting technology. No chemicals are used in the pipeline network water, achieving near-zero discharge of industrial cooling water, balancing water-saving and energy-saving benefits, and extending the service life of the pipeline network. It is suitable for large-scale industrial circulating cooling water treatment, such as in thermal power plants, steel mill cold rolling, petrochemical and pharmaceutical fields.

2. Water-Saving Technology for Textile Dyeing

China's textile dyeing industry consumes about 2.1 billion cubic meters of water annually, of which polyester chemical fiber dyeing consumes 1.6 billion cubic meters, discharging large amounts of high-COD, high-salinity wastewater. Various water treatment devices developed domestically based on active biological bacteria, membrane technology, and electrolysis technology basically meet industry discharge requirements but cannot fully achieve compliant reuse. New technologies and processes aimed at water saving are severely lacking. Polyester chemical fiber waterless dyeing technology uses self-developed nano-coatings, combined with circulating uniform spray, infrared pre-drying, and enclosed high-temperature color fixation processes, to complete the latest dyeing technology. According to the 2017 version of the "Specifications for the Printing and Dyeing Industry" issued by the Ministry of Industry and Information Technology, the upper limit for comprehensive water consumption per ton of fabric dyeing is 140 cubic meters. This technology uses only 0.5 cubic meters of water per ton of fabric dyeing, demonstrating remarkable water-saving and pollution reduction effects.

3. Water-Saving and Emission Reduction Technology for Mining

Mining and mineral processing are national strategic industries. Important non-ferrous metal ores, such as gold, iron, copper, and rare earth ores, mostly use hydrometallurgical processes for beneficiation and smelting. Large amounts of chemicals are added to water to dissolve and extract useful components, discharging large volumes of toxic wastewater and sludge. Reliable and effective water-saving and pollution reduction technologies are urgently needed. In recent years, significant progress has been made in water-saving and pollution reduction technologies for gold ore beneficiation processes. By organically integrating nano-semiconductor electrolysis technology, microporous nano-photocatalytic technology, PE tempered microporous membrane filtration technology, and ultrasonic atomization technology with traditional beneficiation processes, a new water-saving and pollution reduction process for gold hydrometallurgical beneficiation has been successfully developed. Through application in a gold ore beneficiation plant processing 300 tons of ore per day (daily water consumption 2400 cubic meters), water recycling in the beneficiation process has been achieved, with tailings meeting standards for dry discharge (crystal water content <20%), saving over 2000 cubic meters of water daily. It is recommended to increase support for this technology, expand production scale, evaluate the reliability of the technology and the stability of the process, and strive to provide a completely new set of water recycling, water-saving, and pollution reduction technology equipment for mineral processing and metallurgical processes.

4. Coal Mine Water Reuse Technology

Coal is the main form of energy supply in China. 70% of coal mining areas suffer from severe water scarcity. Mining 1 ton of coal requires 2 cubic meters of water. Annual coal mine water discharge amounts to 4.5 billion cubic meters, representing serious water resource waste. Technology and equipment for using treated mine water in coal mining have developed rapidly. Magnetic separation water treatment technology, DTRO flat-sheet membrane technology, and PE tempered microporous membrane filtration technology have all been applied in coal mine water treatment. Among them, the "dual-seed method zero discharge" process technology formed by combining DTRO flat-sheet membrane technology with high-salinity concentration and self-induced crystallization technology has achieved zero discharge of mine water and significantly reduced water treatment costs. Efforts to promote and apply such technologies should be further intensified.

III. Public Institutions and Service Sector

1. Water Supply Network Leakage Control Technology