1、8 . 5 The Relation between Groundwater ，Karst and Soil，Agriculture,Groundwater and Formation and Development of Soil 2. Groundwater and the Agricultural Irrigation 3. Groundwater and the Land Use Planning 4. Groundwater and Salinity , Swamp of Soil 5. Groundwater and Environment 6. The Resources and

2、 Harm of Karst,太行山至濱海平原土壤分布斷面圖,4. Groundwater and Salinity , Swamp of Soil 土壤沼澤化：土壤長期處于過濕狀態(tài)，以致地表滯水，植物遺體因氧化不全而形成泥炭層堆積下來，便形成沼澤。,按補給水源， 有主要由大氣降水補給、 地表水補給、和地下水補給的沼澤。 地勢低洼，或地下水流動受阻，潛水接近地表的地方，可形成潛水補給的沼澤。 治理沼澤的關鍵是排水，排除地表水，有時還需要排除潛水。,土壤鹽漬化：在比較干旱的氣候條件下，由細粒土組成的平原、盆地中，埋藏較淺的潛水強烈蒸發(fā)，鹽分積累于土中的現象。 要防治土壤鹽漬化，也應采取 ，同時沖

3、洗土壤，以排水措施，降低地下水位減弱土壤積鹽過程。,5. Groundwater and Environment 過量開采地下水，引起地下水位持續(xù)下降，形成地下水降落漏斗，從而引起地面沉降,還會引起海水入侵、下水水質污染、地面塌陷等環(huán)境問題。,北方地下水開采最大的河北平原，8093年，累計超采518億m3，年超采約28.78億m3 山東：8493年，累計超采64.37億m3，年超采4.64億m3 北京：8095年，累計超采22.7億m3,北方各省開采地下水總面積65.8萬km2 ; 有16萬km2形成地下水降落漏斗，河北、天津最嚴重。其中 河北1997年，8598 km2 ，衡水市1995年，

4、5668 km2 北京：1995年，1963km2 ， 山東1998年，13501km2,截止到2005年年底，北京市地面沉降量大于50mm的面積達到4114.12km2， 最大累計沉降量1m（1086mm）,地下水位超采，改變了地下水壓力，產生了粘性土釋水及含水層、滯水層壓縮效應，從而導致地面沉降，我國目前已發(fā)現地面沉降城鎮(zhèn)36座。,6. The Resources and Harm of Karst （1）巖溶的資源性（旅游資源） （2）巖溶的危害(石漠化）,云南省富源石漠化景觀,貴州省六盤水石漠化景觀,普定陳旗村喀斯特山地,普定陳旗村小流域地形,1、荔波縣堯古村景觀,2、未石漠化黑色石灰

5、土剖面 （荔波，原始森林）,3、輕度石漠化黃紅壤景觀 （荔波，草地）,1,2,3,4、輕度石漠化黃紅壤土壤剖面（荔波，草地）,4,本章小結 一、基本概念 地下水、重力水、結合水、透水層、含水層、隔水層、硬度、 礦化度、空隙 (孔隙、 裂隙、溶穴) 、潛水、承壓水、孔隙水、裂隙水、巖溶水 包氣帶 飽水帶 巖溶, 峰叢,峰林,溶洞,二 、掌握主要的地下水類型及其特征 1. 按地下水的埋藏條件把地下水分為 包氣帶水土壤水 (Soil water) 上層滯水 perched water 潛水(phreatic water) 承壓水(confined water),2.按含水層空隙性質，把地下水分為：

6、孔隙水(pore water) 裂隙水(fissure water) 巖溶水(Karst water),掌握包氣帶水,潛水, 承壓水,以及孔 隙水,裂隙水和巖溶水的特點,三、 巖溶形成的基本條件 1.巖石的可溶性 2.巖石的透水性 3.水的溶蝕性 4.水的流動性 四、掌握主要的巖溶地貌類型,形成過程及其特征,1.Key terms: groundwater: 地下水 porosity:孔隙度 pore:孔隙 fissures(fractures):裂隙 cavities:溶穴 zone of aeration（包氣帶） zone of saturation（飽水帶）,permeability（

7、滲透性) aquifer（含水層） aquiclude（隔水層） unconfined aquifer（無壓含水層） confined aquifer（承壓含水層） water table（潛水面） spring(泉)，geyser(間歇泉） phreatic water（潛水）, confined water（承壓水）,pore water: 孔隙水 fissure water：裂隙水 Karst, karst water：巖溶水 peak cluster（峰叢）, peak forest（峰林） , isolated peak（孤峰） cave（溶洞）, stalagmite（石筍）, s

8、talactite（石鐘乳） speleothem （洞穴堆積物）,2.English summary: Surface waterflowing in rivers，standing in lakes，or falling as precipitationenters the wherever topography，geological composition，and vegetation cover permit infiltration. The optimal conditions for development of a large reservoir of groundwater

9、include a well-vegetated, gently sloping or near-level landscape composed of fractured bedrock or coarse well-sorted sediment.,Water enters the ground under the influence of gravity, which carries it downward in soil and rock until it fills every available connected pore space. A zone of aeration ne

10、ar the surface may not be water-filled pores. Below it lies the zone of saturation, in which all available pore spaces are water-filled. The upper surface of the saturated zone is the water table. Immediately above the water table, within the zone of aeration, is the capillary fringe, into which wat

11、er rises from the water table duo to the molecular attraction of water molecules and the high pressure in the zone of saturation(compared with the zone of aeration).,Water flows underground when the geological materials are sufficiently porous and permeable. porosity, the percentage of pore space re

12、lative to the total volume of soil, rock, or sediment, is a measure of how much water can held by earth materials. Permeability is a measure of ability of rock or sediment to transmit a fluid; the presence of connected fractures in solid bedrock and the coarse, well-sorted texture of unconsolidated

13、sediment and soil increase permeability.,Aquifers are permeable, water-bearing bodies of geologic materials. Those found at the surface, such as within floodplain deposits and glacial gravels, are not overlain by impermeable cap rock and are called unconfined aquifers. Confined aquifers, found at gr

14、eater depth, are sandwicheed between impermeable rock layers called aquicludes or rock layers of low permeability called aquitards. When an aquifers water is under high pressure from large elevation differences between recharge and discharge sites, the water rises above the level of the aquifer and

15、gushes from the ground.,Geologists describe such self-pumping aquifers as artesian（自流的）. The level to which such pressurized water would theoretically rise, in the absence of friction, is the aquifers potentiometric surface. The regional water table can often be identified from the location of surfa

16、ce-water features such as rivers, lakes, and natural springs, places where the Earths surface intersects the water table and groundwater flows out without human assistance. By drilling test wells, and with the knowledge,that the water level in wells approximates the local groundwater table, geologis

17、ts can estimate the location of the regional water table. Human activity can disturb the groundwater system through overwithdrawal and contamination. In areas experiencing rapid growth and where formerly rural land has become suburban or urban, increased population and industrial development cause g

18、roundwater demand to rise sharply, and the water table may drop significantly. Large cone of depression, local depressions in the,Water table, develop around wells. Lowered water tables make it necessary to dig deeper wells at higher costs. They also promote subsidence of the land surface as deplete

19、d aquifers become compressed.In coastal regions, excessive groundwater withdrawal may cause salt water to infiltrate subsurface aquifers.,Karst terrains develop from the dissolution of soluble bedrock. Most karst is the result of the dissolution of calcite in limestone by carbonic acid. Dissolution

20、rates are largely controlled by the composition and structure of the bedrock, the amount of rainfall and vegetation in the area, and local topography. Karst terrains contain both subsurface and surface features not found in any other geological setting. Extensive cave systems are often found below t

21、he surface of a karst landscape. Cave s are natural underground cavities that generally form,as carbonate bedrock dissoves along preexisting joints, fractures, faults,and bedding planes. Most caves develop by a two-stage process: In the first stage, the local water table is high; cave chambers and c

22、onnecting passageways form from a system of water-filled bedrock fissures. In the second stage, the water table has dropped, and because the cave is now located above the water table, its rooms and passageways exist in an open-air environment. As water that percolates through overlying bedrock enters the cave, it can evaporate or,release its carbon dioxide, both of which result in dissolved limestone being precipitated. Cave deposits, called speleothems, i