| At present,under the background of"more people and less water"in Beijing,According to the2018 Water Resources Bulletin published by the Beijing municipal water bureau,the proportion of environmental water in urban water use is still large,accounting for 33.8%,and the urban green area is still on the rise.By the end of 2018,the green area is 85286.37 hm2,so green land irrigation water has become a major problem.Between April and September of 2019,Based on the field investigation and data statistical analysis,this paper makes a comparative analysis of the actual irrigation water consumption of green land irrigation sources,plant allocation mode,irrigation mode and green land type,objectively evaluates the current situation of green land irrigation water in Beijing,finds out the existing problems,and puts forward reasonable suggestions.At the same time,based on the soil water threshold value summarized by the predecessors,this paper makes a comparative analysis of the actual irrigation water consumption of green land irrigation sources,plant allocation mode,irrigation mode and green land type According to the water-saving irrigation system suitable for Beijing green land irrigation,the water-saving potential of Beijing green land irrigation is calculated.The main results are as follows:?1?Total annual irrigation water consumption of different irrigation water sources:the total amount of tap water irrigation water is 266.5 million m3?The ratio is 92.22%?;the total amount of underground water irrigation water is 11.7 million m3?The ratio is 4.04%?;the total amount of reclaimed water irrigation water is 10.8 million m3?The ratio is 3.74%?;the total amount of irrigation water is 289million m3.At present,Beijing is mainly irrigated by tap water,and the proportion of irrigation water consumption is 92.22%.The water consumption of different irrigation water sources is mainly related to the configuration of underground water pipeline in Beijing,the popularization rate of reclaimed water treatment equipment and the proportion of reclaimed water used in garden and green land irrigation.?2?The total amount of irrigation water in different plant configuration modes:the total amount of irrigation water in arbor,shrub and grass configuration mode is 106.6 million m3?The ratio is36.89%?;the total amount of irrigation water in arbor and shrub configuration mode is 48.7 million m3?The ratio is 16.83%?;the total amount of irrigation water in arbor and grass configuration mode is48.7 million m3?The ratio is 16.84%?,The total amount of water used for arbor irrigation is 25 million m3?The ratio is 8.65%?,for grass irrigation is 26.4 million m3?The ratio is 9.14%?,for shrub and grass configuration mode irrigation is 24.5 million m3?The ratio is 8.49%?,and for shrub irrigation is 9.1million m3?The ratio is 3.16%?.At present,the main irrigation water consumption mode in Beijing is arbor,shrub and grass configuration mode,and the proportion of irrigation water consumption is36.89%.The total amount of irrigation water in different plant allocation models is mainly related to the proportion of area,the type of green space and the corresponding irrigation methods.The annual irrigation water consumption per unit area of different plant allocation modes:3097.78 m3·hm-2 for arbor,shrub and grass configuration,3726.02 m3·hm-2 for arbor and shrub configuration,3542.29m3·hm-2 for arbor and grass configuration,3405.61 m3·hm-2 for arbor,4204.35 m3·hm-2 for lawn,3788.85 m3·hm-2 for shrub and grass configuration,and 2783.52 m3·hm-2 for shrub.Because there are many types of green space suitable for compound green space,combined with the annual irrigation water consumption per unit area,the optimal allocation mode of water-saving plants in the actual green space irrigation is selected as arbor,shrub and grass configuration.?3?The total annual irrigation water consumption of different irrigation methods:the total water consumption of sprinkler irrigation is 76.8 million m3?The ratio is 26.57%?;the total water consumption of micro sprinkler irrigation is 39.9 million m3?The ratio is 13.81%?;the total water consumption of artificial water pipe irrigation is 94.8 million m3?The ratio is 32.80%?;the total water consumption of water truck irrigation is 77.5 million m3?The ratio is 26.82%?.At present,Beijing is still dominated by traditional irrigation.The total amount of annual irrigation water for different irrigation methods is mainly related to the area of different irrigation methods used by green land and the popularity of water-saving irrigation equipment.The average annual water consumption per unit area of different irrigation methods:3275.63 m3·hm-2 for sprinkler irrigation,3265.16 m3·hm-2 for micro sprinkler irrigation,4253.00 m3·hm-2 for artificial water pipe irrigation,3951.76 m3·hm-2 for water truck irrigation.In addition to considering the actual irrigation water consumption,the selection of the optimal irrigation mode also needs to be combined with the actual situation.Because there are problems such as the supply pipeline in the irrigation of micro sprinkler irrigation,and the difference between the micro sprinkler irrigation and the sprinkler irrigation water consumption is negligible,the optimal irrigation mode in the actual irrigation is finally selected as sprinkler irrigation.?4?Total annual irrigation water consumption of different types of green space:93 million m3 for park irrigation?The ratio is 32.16%?;4.5million m3 for community park irrigation?The ratio is 1.55%?;14.2 million m3 for roadside green space irrigation?The ratio is 4.92%?;27.6 million m3 for other park green space irrigation?The ratio is 9.53%?;2.7 million m3 for production green space irrigation?The ratio is 0.94%?;38 million m3 for protection green space irrigation?The ratio is 13.15%?;40.2 million m3 for residential green space irrigation?The ratio is 13.92%?;The total amount of road green land irrigation water is 33.7 million m3?The ratio is 11.67%?,and the total amount of unit green land irrigation water is 35.1 million m3?The ratio is 12.16%?.At present,the irrigation water consumption of parks is the largest among all green land types in Beijing,accounting for 32.16%.The irrigation water consumption of different green land types in each district is mainly related to the area of green land types,management units and corresponding maintenance requirements.Among the annual irrigation water consumption per unit area of different types of irrigation green land,the maximum irrigation water consumption per unit area of the park is 4524.79 m3·hm-2,and the minimum irrigation water consumption per unit area of protective green land is 2243.13 m3·hm-2.?5?Water saving potential of green land irrigation in urban area of Beijing:the actual irrigation water consumption in Beijing is 289 million m3.Based on the threshold value of soil moisture,the total amount of irrigation water for each maintenance level under the water-saving irrigation system is 122.2million m3,with 80%of the irrigation water use efficiency of sprinkler irrigation,the total amount of irrigation water for maintenance level under the water-saving irrigation system is 152.8 million m3;finally,the water-saving potential of Beijing urban green land irrigation is 136.2 million m3,with 47.13%of the water-saving rate.At present,the efficiency of irrigation water use is about 52.87%,which is expected to increase to 80%and 27.13%after water-saving irrigation. |
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