The Relationship Between Evolution Of Shallow Groundwater Recharge,Discharge System And Attenuation Of Karez Flow In Gaochang District,Turpan City

Taking shallow groundwater recharge, discharge system and Karez flow as research subjects in Gaochang District of Turpan, based on the former research results, such as monitoring data, field investigation and survey results, using GIS, PMWIN, GMS, and SUFER software, the influence of evolution of shallow groundwater recharge, discharge system on attenuation of Karez flow was studied, the varition of Karez flow was predicted, and the reasonable groundwater exploitation was proposed on the premise of protecting Karez. Some results as follows:(1) In the shallow groundwater recharge and discharge system, there were no obvious changes in the lateral recharge, the river leakage reduced in power function, the channel seepage firstly increases and then inclined to a stable value, followed by a downward trend, irrigation return infiltration, reservoirs and ponds leakage and the exploitation of water wells showed a downward trend after the firstly increase, and there was a gradual reduction of both shallow water evaporation and lateral discharge.(2) Karez flow is mainly affected by river leakage, channel seepage and well production. According to their impact, they are arrayed in a descending order as: well production, river leakage, and channel seepage. The decrease of Karez flow can be caused by the increase of well production and the decrease of river leakage.(3) There is a basically linear relationship between well production and Karez flow show, which means the more the water wells is exploited, the faster Karez flow reduces. Taking the exploitation(2.61×108m3) of 2014 as the reference value, when it increased by 10%, 20%, 30%, 40%, and 50%, Karez flow accordingly reduced 4.44%, 7.31%, 11.94%, 16.03 %, and 18.75%, and when it decreased by 10%, 20%, 30%, 40%, and 50%, Karez flow increased by 2.11%, 3.55%, 5.05%, 7.31%, and 8.07%, respectively. Moreover, while there is the same rangeability of well production, there is different rangeability of Karez flow. Karez flow declined quickly with the increment of Well production while Karez flow recovered slowly with the reduction of well production, which means Karez flow declines easily, but it is difficult to recover.(4) If underground water continues to be over-exploited annually according to the exploitation(2.61×108m3) of 2014 in Gaochang District of Turpan City, the underground water level will expeience a sustained decline, and Karez flow would be left only 3095×104m3 by 2030, decreasing by 24% compared with 2014. If underground water continues to be exploited annually as the exploitable quantity of 2.04×108m3by 2030, underground water level wolud have no obvious decrease and Karez flow would be 4283×104m3,increase by 5% compared with 2014. If underground water continues to be exploited according to the control of “three red lines”, by 2030, underground water level would rise in most areas compared to 2014, and Karez flow would return to 5360×104m3as well, increasing by 31% compared with 2014.(5)If the current Karez flow in Gaochang District of Turpan City is expected to be prevented from declining, the reasonable exploitation of groundwater should be kept at approximately 2.04×108m3; if we exploit groundwater according to the control of “three red lines”, the Karez flow could constantly recover, owning to which the groundwater resources will be 1.82×108m3 to 2020 and 1.58×108m3 to 2030.