| Water system connectivity and water resources security is one of the hotspots of water science research at present.In order to find out the relationship between river-lake water system connectivity and water resources in the three outlets of South of Jingjiang River,and screen the strategic measures for water resources security,the water resources situation under the variation of water system connectivity and the regulation scheme based on water resources security are studied from the perspective of water system connectivity by mathematical statistics and system dynamics.The following conclusions are drawn:(1)From 1956 to 1989,the river system connectivity in the three outlets of South of Jingjiang River showed a downward trend,with a total decline of 23.88%.From 1990 to 2017,the river system connectivity showed a slow upward trend,with a total increase of less than 0.5%.There is the minimum value of river system connectivity in1989,which is the variation point of water system connectivity in this area.The study period is divided into two periods.The first is 1956-1989 before variation,and the second is 1990-2017 after variation.(2)After the water system is connected and changed,the time and space change of water resources in this area are significantly different.After the variation,the amount of water resources showed a significant downward trend,and the annual linear decline rate was about 7.39×10~8m~3/a.The sharp decline trend was obvious during the flood season,but the water resources in the flood season were more concentrated,accounting for 70%of the total amount.Water resources during the dry season was very lack.Flow in the east branch of the Ouchi River was cut-off for 5 months,and the annual average water resources was reduced by 208.32×10~8 m~3.The time period of alternating abundance and drought was shortened by 1~13a,the time scale of the strongest periodic oscillation decreased from 28a to 15a and the number of oscillations was increased by 1 to 3 times.In space,there exited a significant downward trend in the west branch of the Songzi River,the Hudu River,and the east branch of the Ouchi River and the degree of decline was different after variation.The days of the cut-off reached to 267 days in the east branch of the Ouchi River.(3)The hydrological and drought characteristics of this area were obvious after variation of river system connectivity.After variation,the average annual occurrence frequency of hydrological drought increased to 1.22-2.7 times,and the average duration of hydrological drought increased by about one month.The average increase values of hydrological drought intensity at five stations were 104.53×10~8m3,57.58×10~8m3,80.75×10~8m3,18.15×10~8m3and 105.91×10~8m3respectively.The average value of hydrological drought peak increased too.After variation,the two-dimensional combined recurrence period of hydrological drought characteristics was shorten.The drought duration of the same single variable recurrence period was longer,the drought intensity was greater and the peak value was higher.In 2006(dry year),the water shortage in five stations were 13.82×10~8m3,5.08×10~8m3,6.50×10~8m3,14.2×10~8m3and 9.81×10~8m3respectively.(4)There is a mutual influence and mutual restriction relationship among water system structure,water system connectivity and water resources.The Pearson correlation coefficient between the parameters of the water system structure and the water system connectivity was0.76~0.88,the water system connectivity value was in the range of0.0138~0.1857.Water system connectivity and river length,water surface rate,river frequency,river network density,river network.The connectivity of water system increased linearly with the parameters of river structure such as length,water surface ratio,River frequency,network density,network development coefficient and fractal dimension coefficient.The Pearson correlation coefficient between water system connectivity and water resources was 0.78,and the water system connectivity and water resources showed a linear growth trend.(5)Based on DYNAMO language and Vensim analysis software,the dynamic model of water resources security control system(SD)was constructed in three outlets area of south of Jingjiang.Water resources were simulated by SD model in four schemes of status quo continuation,resource saving,economic development and comprehensive coordination.The supply and demand differences of water resources in the short-term and long-term were-1.44×10~8m~3 and-0.93×10~8m~3 respectively under the comprehensive coordination pattern.The water resources had surplus.The long-term total population were more 33,600 and 51,100 respectively in the comprehensive coordination pattern than those in the status quo continuation pattern and resource saving pattern.Similarly,the industrial output values were more 5.528 billion yuan and 5.572 billion yuan respectively,the industrial output values of the tertiary industry were more 206 million yuan and 3.408 billion yuan respectively,the livestock volumes were more 325,500 heads and 415800 heads respectively,and the irrigated areas of farmland irrigated area were more 171.2 million mu and174.9 million mu respectively.The fourth scheme was the optimal plan for water resources security regulation in the region because of maximal water resources benefits and the highest comprehensive evaluation.The comprehensive coordination model was a optimal model for achieving water security in the region.(6)Specific measures were proposed to realize comprehensive development model based on water resources security.Water system connectivity engineering and water source engineering can be implemented,and“multi-source complementary,abundant and dry adjustment”water supply project management system can be established.Other measures include industrial structure adjustment and upgrading,water resources industry Reasonable allocation,efficient water conservation in agriculture,improving water efficiency in the national economy,increasing wastewater reuse rate,and reuse of industrial water. |
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