water consumption[1]It refers to the actual water consumption of soil under certain water conditions.It usually includes the actual transpiration water consumption of plants, as well as the water loss due to evaporation or lower layer leakage.When soil water condition is optimal, plant water consumption and water demand are consistent;When water leakage is 0, water consumption is consistent with plant transpiration.
Chinese name
water consumption
Foreign name
Water consumption
Field
Ecological engineering
Discipline
environmental science
Interpretation
Actual water consumption of soil under certain water conditions
Water consumption is the total water consumption in farmland during the whole growth period of crops from sowing to harvesting.For dry landCrop water demandAnd the amount of deep seepage water.However, under the condition of implementing water-saving irrigation technology, the amount of deep leakage can be ignored;For paddy field, its value is equal to the sum of water demand of rice and seepage of paddy field.It is the basic data of irrigation area planning, design and planned water use[2]。
The soil plant atmosphere system (SPAC) is the most intense active layer of energy cycle and material transformation in the earth's surface.In this system, water movement is the most active, and vegetation transpiration and soil evaporation (collectively called evapotranspiration) play an extremely important role in the process of water movement. It is not only an important part of water balance, but also an important part of energy balance. At the same time, it is closely related to the physiological activities of plants and the formation of biomass.Therefore, the research on evapotranspiration has always been an important topic of common concern in the related disciplines and fields such as agronomy, meteorology, hydrology, soil and physical geography.Comprehensively understanding the rule of evapotranspiration and selecting appropriate methods to calculate evapotranspiration water consumption of farmland and forest land are of great significance and role for the development of water-saving agriculture, strengthening the intensive management of water resources, improving water use efficiency and simulating and forecasting biological yield.
With the rapid increase of population and global warming, the shortage of water resources has become a global environmental problem. It is imperative to strengthen the scientific management and rational use of water.Therefore, the research work of evapotranspiration calculation method will get more and more attention.
Calculation of water consumption by hydrological method
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Hydrological method is to study regional erosion characteristics based on hydrological characteristics[3]。This method indirectly measures the total evapotranspiration based on the water balance of a certain area and soil depth in a certain period of time, so it can also be called "water balance method".The measured spatial scale can be as small as a few square meters and as large as dozens of square kilometers.For water balance method, the time scale shall be more than one week.The measurement error caused by the spatial variability of each balance component will be concentrated on the total evapotranspiration, which will affect the calculation accuracy.In the forest with large soil space and distant trees, more measuring points are needed to ensure the accuracy of evapotranspiration measurement.The biggest advantage of this method is that it is not limited by meteorological conditions.The disadvantage is that the measurement time is relatively long, so it is difficult to reflect the daily dynamic change of evapotranspiration.
Plant Physiology
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The plant physiology method is mainly used to measure the water consumption of a part or the whole plant, and can be used as an auxiliary method to analyze the relationship between plant and water.It mainly includes: rapid weighing method, stomatometer method, wind chamber method, isotope tracing method and thermal pulse method.In some special cases, such as complex terrain, isolated small pieces or single plants, only physiological methods can be used to estimate transpiration.In China, this method is commonly used to measure or calculate tree transpiration.The main disadvantage is that because of the representativeness of the sample, it is difficult to accurately calculate the total transpiration of a large area of plants from the transpiration of a single plant or several plants[4]。
Future Outlook
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(1) Vegetation evapotranspiration is a complex physical and biological process, and has become one of the important research contents of international projects such as the International Hydrological Program (IHP), the International Geosphere Biosphere Program (IGBP), the World Climate Research Program (WCRP), the United Nations Environment Program (UNEP), and the Global Water and Energy Balance Program (GEWEX).The joint research of multiple disciplines and departments is the main way and direction of future research on evapotranspiration.
(2) Under the condition of uniform underlying surface, especially in the crop ecosystem, the calculation method of evapotranspiration has been studied and improved by scholars in past dynasties, and some experiments or calculation models with relatively stable experimental results have been produced.However, under the condition of non-uniform underlying surface, the interaction between vegetation and environment and between vegetation is more complex than that of uniform underlying surface.Therefore, the research in this area will become the focus of future evapotranspiration research.
(3) With the development of science and technology, the continuous emergence of automatic and high-precision observation instruments will provide a strong technical guarantee for the improvement of evapotranspiration calculation methods.
