第8-5 地下水、岩溶与农业资源.ppt

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,太行山至滨海平原土壤分布断面图,4. Groundwater and Salinity , Swamp of Soil 土壤沼泽化：土壤长期处于过湿状态，以致地表滞水，植物遗体因氧化不全而形成泥炭层堆积下来，便形成沼泽。,按补给水源， 有主要由大气降水补给、 地表水补给、和地下水补给的沼泽。 地势低洼，或地下水流动受阻，潜水接近地表的地方，可形成潜水补给的沼泽。 治理沼泽的关键是排水，排除地表水，有时还需要排除潜水。,土壤盐渍化：在比较干旱的气候条件下，由细粒土组成的平原、盆地中，埋藏较浅的潜水强烈蒸发，盐分积累于土中的现象。 要防治土壤盐渍化，也应采取 ，同时冲

3、洗土壤，以排水措施，降低地下水位减弱土壤积盐过程。,5. Groundwater and Environment 过量开采地下水，引起地下水位持续下降，形成地下水降落漏斗，从而引起地面沉降,还会引起海水入侵、下水水质污染、地面塌陷等环境问题。,北方地下水开采最大的河北平原，8093年，累计超采518亿m3，年超采约28.78亿m3 山东：8493年，累计超采64.37亿m3，年超采4.64亿m3 北京：8095年，累计超采22.7亿m3,北方各省开采地下水总面积65.8万km2 ; 有16万km2形成地下水降落漏斗，河北、天津最严重。其中 河北1997年，8598 km2 ，衡水市1995年，

4、5668 km2 北京：1995年，1963km2 ， 山东1998年，13501km2,截止到2005年年底，北京市地面沉降量大于50mm的面积达到4114.12km2， 最大累计沉降量1m（1086mm）,地下水位超采，改变了地下水压力，产生了粘性土释水及含水层、滞水层压缩效应，从而导致地面沉降，我国目前已发现地面沉降城镇36座。,6. The Resources and Harm of Karst （1）岩溶的资源性（旅游资源） （2）岩溶的危害(石漠化）,云南省富源石漠化景观,贵州省六盘水石漠化景观,普定陈旗村喀斯特山地,普定陈旗村小流域地形,1、荔波县尧古村景观,2、未石漠化黑色石灰

5、土剖面 （荔波，原始森林）,3、轻度石漠化黄红壤景观 （荔波，草地）,1,2,3,4、轻度石漠化黄红壤土壤剖面（荔波，草地）,4,本章小结 一、基本概念 地下水、重力水、结合水、透水层、含水层、隔水层、硬度、 矿化度、空隙 (孔隙、 裂隙、溶穴) 、潜水、承压水、孔隙水、裂隙水、岩溶水 包气带 饱水带 岩溶, 峰丛,峰林,溶洞,二 、掌握主要的地下水类型及其特征 1. 按地下水的埋藏条件把地下水分为 包气带水土壤水 (Soil water) 上层滞水 perched water 潜水(phreatic water) 承压水(confined water),2.按含水层空隙性质，把地下水分为：

6、孔隙水(pore water) 裂隙水(fissure water) 岩溶水(Karst water),掌握包气带水,潜水, 承压水,以及孔 隙水,裂隙水和岩溶水的特点,三、 岩溶形成的基本条件 1.岩石的可溶性 2.岩石的透水性 3.水的溶蚀性 4.水的流动性 四、掌握主要的岩溶地貌类型,形成过程及其特征,1.Key terms: groundwater: 地下水 porosity:孔隙度 pore:孔隙 fissures(fractures):裂隙 cavities:溶穴 zone of aeration（包气带） zone of saturation（饱水带）,permeability（

7、渗透性) aquifer（含水层） aquiclude（隔水层） unconfined aquifer（无压含水层） confined aquifer（承压含水层） water table（潜水面） spring(泉)，geyser(间歇泉） phreatic water（潜水）, confined water（承压水）,pore water: 孔隙水 fissure water：裂隙水 Karst, karst water：岩溶水 peak cluster（峰丛）, peak forest（峰林） , isolated peak（孤峰） cave（溶洞）, stalagmite（石笋）, s

8、talactite（石钟乳） speleothem （洞穴堆积物）,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