Research And Development Of Rainwater Harvesting Device Based On Subsurface Irrigation With Ceramic Emitters

Mineral resources are an important material foundation for human survival and development.However,due to the extensive exploitation of mineral resources over the years,the ecological environment of numerous mining land has been severely damaged,which seriously affects industrial,agricultural production and human settlement.Ecological forest restoration serves as a critical approach to realizing ecological restoration in the mining area.However,drought and water shortage restrict the survival rate of the ecological forest.At present,rainwater harvesting and supplemental irrigation is one of the effective ways to improve the survival rate of ecological forests.Nevertheless,the existing supplemental irrigation of harvested rainwater technologies have either low rainwater utilization efficiency or high investment cost.Thus,the study of new cheap rainwater harvesting supplementary irrigation device can improve the efficiency of rainwater utilization and the survival rate of ecological forest in mining area.Therefore,a new rainwater harvesting device with subsurface irrigation using ceramic emitters is developed.On the basis of rainwater resource collection,the device combines the advantages of microporous ceramic emitter developed by the research group.By analyzing the rainfall characteristics of typical dry region and the water requirement of conventional ecological forest tree species,the key structural parameters of the device were determined,including the area of the rainwater collection plate,the volume and height of the water storage tank,the length of the bottom side,the burial depth of the emitter,and the diameter of the ceramic seepage patch.Finally,the application effect experiment of the rainwater harvesting device with subsurface irrigation using ceramic emitters.Taking the soil moisture environment and the growth of Platycladus orientalis as the evaluation indicator,combined with cost analysis,the application effect and promotion value were evaluated.The following main conclusions were listed as follows:（1）A new rainwater harvesting device with subsurface irrigation using ceramic emitters is developed.The device is mainly composed of rainwater collecting plate,water storage tank and self-developed button microporous ceramic emitter.The material of rainwater collecting plate is PVC,and the shape is designed to be funnel-shaped.The plate surface is equipped with multiple water dividing slots with a depth of 3 cm.and the plate surface is surrounded by 10 cm above the ground to prevent sand and dust from entering the water storage tank.The water storage tank is made of polypropylene and designed in the shape of a four-edged platform.While a circular hole is reserved in the middle of the storage tank to facilitate for planting tree.The button type ceramic emitter is mainly composed of ceramic seepage patch,plastic rubber washer,upper sealing cover,and lower sealing cover.The water first enters the internal cavity of the ceramic emitter from the upper sealing cover.Then the water seeps through the pores inside the ceramic seepage patch and penetrates into the soil from the lower sealing cover.In particular,this study independently developed two kinds of button-type ceramic emitters,which are clay-base and quartz-base.The rated flow ranges of the two ceramic emitter are 15.1～28.2 ml h^-1 and 99.2～221.2 ml h^-1 respectively.The flow rate of the emitter can be controlled by adjusting the diameter of the ceramic seepage patch.（2）The critical parameters of rainwater harvesting device with subsurface irrigation using ceramic emitters have been preliminarily determined.Taking the rainfall data of three typical arid areas（Wuhai City,Urad Front Banner and Lanzhou City）as the object.The interannual and monthly rainfall distribution laws of typical arid areas were analyzed by rainfall concentration index（PCI）,standardized precipitation Index（SPI）and relative variability of monthly rainfall（V）.Furthermore,considering the monthly water demand,daily water demand,extreme rainfall days of trees,and collecting more than 90%of the annual effective daily rainfall conditions,the appropriate area of rainwater collecting plate and water storage tank are determined to be 1 m² and 25 L.The spatial and temporal distribution of wetted bodies formed by button ceramic emitters under different working heads and soil texture conditions was studied.Combined with the root distribution characteristics of typical ecological forest species,the height of water storage tank,bottom side length,and buried depth of emitter were determined to be 20 cm,32 cm and 10 cm,respectively.Finally,it is analyzed that the water requirement of different ecological forest species is mainly between 3.6 ml h^-1 and 22.1 ml h^-1.In order to adapt the water requirement of tree species and control the mold opening cost,the diameter of ceramic seepage patch is recommended to be22.5 mm.（3）The use of rainwater harvesting device with subsurface irrigation using ceramic emitters can maintain a stable soil moisture environment,promote the growth of sideburn.The soil moisture content in the root zone of Platycladus orientalis can be stabilized at 21.6%～24.0%for a long time by by using rainwater harvesting with subsurface irrigation using ceramic emitters.The coefficient of variation of soil moisture content is 0.038,forming a stable soil moisture environment.Furthermore,compared with the natural growth of the cypress,rainwater harvesting with subsurface irrigation using ceramic emitters can increase the plant height of the Platycladus orientalis by 7.1 cm,the crown width by 4.2 cm,the new branch length by 3.8 cm,and the ground diameter by 0.48 mm.Finally,compared with the afforestation cost of artificial sprinkler,rainwater harvesting with subsurface irrigation using ceramic emitters can reduce afforestation costs by 240.2 CNY ha^-1,with a reduction rate of 11.5%.In this study,a new rain harvesting and irrigation device with low cost and reliable effect is proposed,which can provide important technical support for the restoration of green in northwest mining area.