|題名||高屏溪流域中上游地下水及伏流水調查及開發評估Groundwater and Interflow in Middle and Upstream of Gaoping River Basin
|英文摘要||This project collated several major factors of wate resources such as use of water resources, water withdrawals of water supplied facilities and planning water resources construction. The development standard groundwater level were caculated by standard groundwater level index, SGI, and residual stream flow. Then these restrictions were used to limit groundwater exploitation and calculated groundwater, subsurface water resources under controlled impact. Next work was to eatimate benefits in terms of groundwater, subsurface water resources in order to complete the assessment of groundwater and subsurface water resources in middle and upper Gaoping River.
1. Basic Information Collection
(1) Meteorological, hydrography, geology information and use of water resources, water withdrawals of water supplied facilities, planning water resources construction data were collected in this project. The exploitation of surface was 1.25billion tons and groundwater is 0.11 billion tons in Gaoping watershed during 2011 to 2015.
(2) Total 6 meeting were held to collect suggestion from NGOs that consolidated as follows :
(a)Water resources protection is priority.
(b) People’s livelihood water is priority in water supply.
(c)The exploitation of existing wells should be investigated in order to management effectively in groundwater.
(d)Taiwan Water Corporation should ensure the deep groundwater pumping would not effect existing local groundwater supply in Ligang.
(e) NGOs had a neutral stance on results of this project and reservations in water development of project area.
2. Investigation in-situ
(1) Groundwater is the major recharge souce of stream before April and this trend reversed in wet season durig May to October. Then groundwater recharge to stream after wet season in the area of Ligang Bridge, Gaoshu Bridge and Gaomei Bridge.
(2) Right bank of Laonong River from Gaomei Bridge to Ligang Bridge and Left side of Ailiao River at Gaoshu Bridge are the major area that stream recharge to groundwater.
(3) Then mass balance of water chemistry is applied to calculate the exchange between surface water and groundwater in chosen area. The result showed totally groundwater recharge to stream, therefore the variation is high in different years.
3. Restrictive Exploitation of Groundwater
(1) The development standard groundwater level were caculated by standard groundwater level index, SGI, and residual stream flow. Then these restrictions were used to limit groundwater exploitation and calculated groundwater, subsurface water resources under controlled impact.
(2) The restrictive exploitation of groundwater is higher in downstream in project area that near Liling Bridge, because of recharge by stream water. Therefore the reduction of groundwater level makes groundwater resources decreased, so that variation of exploitation is huge in different years.
4. Restrictive Exploitation of Subsurface Water and Benefits of Water Development Ccases
(1) The SGI360 groundwater level and residual stream flow were applied to estimate the restrictive exploitation of subsurface water in 14 locations.
(2) The relations between exploitation and impact of stream waterand groundwater were estimated by numerical models and applied to inverse the restrictive exploitation of subsurface.
(3) The benefits of water resources development were calculate by additional supply in Gaoping Weir, icrease storage of Nanhua reservoir, water support to Tainan system and increased discharge of Gaoping Weir.
(4) The benefits of cases thar include subsurface water, groundwater and integrated cases were calculated in Figure.1. The suggestion location of different cases were listed as follows:
(a) Location of case with 0.1 and 0.2 million tons subsurface waterper day is at Liling Bridge.
(b) Locations of case with 0.3 million tons subsurface waterper day are at Liling Bridge (0.2 million tons) and Bridge of freeway No. 10 (0.1 million tons).
(c) Locations of integrated case with 0.3 million tons that are at Liling Bridge (0.2 million tons subsurface water) and Bridge of freeway No.10(0.1 million tons groundwater).
5. Integrated case with 0.2 million tons subsurface water and 0.1 million tons groundwater has best benefit, thought groundwater level in dry years would limit exploitation of groundwater. So the subsurface water case with 0.3 million tons exploitation is the suggested proposal.