Karst Waters Help Resolving Drought
in Northwest China’s Arid Region
Major breakthrough have achieved in finding deep buried karst water in
a Northwest China’s Special Program of Groundwater Resources. The Program started two
years ago was carried out by the former Ministry of Geology and is now succeeded by the
Ministry of Land and Resources. It is supported directly by the State Council.
Fig.1 Location of exploration
wells with high yield karst water
The findings are at the eastern part of Northwest China’s Arid
Region. It is in the neighbouring areas of Ningxia, Nei Mongol , Shaanxi, Gansu Provinces
(or Autonomous Regions), and characterized by extensive Loess cover hundreds meters thick
(Fig.1). It is thus called as Loess Plateau covering some 200,000 km2, and is
the broadest of this kind of landscape in the world. In the north of the Great Wall, there
is a 20,000 km2 Mu Us Desert. Geotectonically, it is underlain by the Ordos
platform, where Lower Paleozoic carbonate rocks (Cambrian and Ordovician) are overlain
disconformably by Permo-Carboniferous Coal measures , followed by Mesozoic Red Beds,
Neogene Red Clay and Quaternary loess. The paleokarst on the surface of lower Paleozoic
carbonate rocks is one of the most important natural gas reservoirs in China .
The southern part of the Loess Plateau is bordered by the active
Wei River Graben, where geothermal springs are often seen, and frequented by earthquake.
The Wei River Plain is the cradle of ancient China’s culture, with its Xian city as
the historical capital of many Dynasties.
The Loess Plateau has long suffered from water shortage because of low
annual rainfall ranging between 500mm at South (Xian) and less than 200mm at the North (Mu
Us Desert), and bad water quality of shallow aquifers.
Fig.2 Hydrogeological cross
section of Well No.Y1,Fuping, Shaanxi
The first breakthrough happened in early 1997, when the Y1
exploration well completed in Fuping County at the southern part of the Loess
Plateau(Fig.1). It is 778m deep, but 200m are in Loess, with an addition of 300m in
Neogene clay and gravel. 238m of the lower part in the well are in Ordovician Limestone
Karst Aquifer (Fig.2). Pumping test gives a discharge of 5320m3 per day, with a
drawdown of only 1.89m (Fig.3). The potential yield of the well is estimated to be 13300m3
per day. The TDS is 1.18g/L, while the water temperature is 43° V( |