該區(qū)土壤表層的鹽分除了當?shù)爻赏聊纲|(zhì)自然形成的之外

1、該區(qū)土壤表層的鹽分除了當?shù)爻赏聊纲|(zhì)自然形成的之外，很大一部分來自于灌溉水，也就是黃河水。因此，研究黃河水的含鹽量對明確當?shù)毓鄥^(qū)鹽堿形成的原因有重要作用。該區(qū)黃河水的含鹽量約為0.4-1.7g/L，PH值約在8.1-8.8之間，主要包括Na+、Mg2+、K+、Ga2+、SO42-、Cl-、HCO3-、CO32-等離子，其中Na+約為40mg/L，占離子總量的10%。灌溉后，由于強烈的蒸發(fā)，一部分鹽分被留在了農(nóng)田之中，據(jù)研究，該區(qū)僅有不到70%的鹽分被排出，30%的鹽分都積存在了灌溉農(nóng)田里，農(nóng)田平均積鹽3thm²。Saline on the topsoil in this region

2、comes from naturally formed local soil parent materials ,but mostly from irrigation waterwater from Huang He River(yellow river) ,therefore, to better understand how saline and alkaline in the soil of the region have formed ,studying saline and alkaline in the soil of this region is extremely import

3、ant .Water from Huang He River, whose salinity stands at 0.4-1.7g/L and PH value ranges from 8.1 to 8.8,mainly consists of ions ,such as Na+、Mg2+、K+、Ga2+、SO42-、Cl-、HCO3-、CO32-, .Of these, Na takes up 40mg/L, ten percent of the total ion amount. After irrigation, a portion of salt remains in farmland

4、s because water evaporates quickly. It has been studied that salinity in farmlands averages 3thm²,because less than 70 percent of salinity has been discharged while 30% has remained in the irrigated farmlands 灌水攜帶的泥沙及其產(chǎn)生的灌溉淤積物主要危害就在于造成灌溉農(nóng)田的沙化，且淤堵渠道，不僅占用部分良田，還將會造成當?shù)厣衬?，出現(xiàn)澇堿。據(jù)研究，該區(qū)黃河水含沙量約為100-400

5、kg/m³，進一步加劇了該區(qū)農(nóng)田的沙化和鹽漬化，但是，如果運用得當，泥沙也會改善當?shù)氐耐寥览砘再|(zhì)，改善土壤孔隙狀況，提高農(nóng)田土壤肥力。Silt carried by irrigating water and deposited sediments caused by irrigation, which intensify irrigated farmlands desertification and block irrigation channels, not only take up some fertile farmlands, but cause local region d

6、esertified and waterlogging . The study shows that sands in Huang He River approximately have reached 100-400kg/m³,which makes farmlands more desertifying and salinizing. But if used properly, silt can change soil properties, improve the condition of soil pores and make farmlands more fertile地下

7、水中的鹽分和底土中的鹽分是土壤表層積鹽的主要來源，因此，地下水位抬高是該區(qū)鹽堿的主導因素，而地下水位的升降與灌溉密切相關。據(jù)研究，該區(qū)灌水期比非灌水期地下水位升高0.85-1.32m，且表層土壤鹽分隨灌溉量增大而加劇。由于該區(qū)灌溉主要依靠引進大量黃河水，忽視地下水的開采利用，導致地下水位連年上升。目前研究認為，該區(qū)地下水位臨界值在1.5-2.4m，超過此值，易發(fā)生鹽堿，目前該區(qū)地下水位多在2-5m之間。該區(qū)地下水含鹽量不均衡，重度一般在10g/L，也有的區(qū)域小于1 g/L。主要離子為Na+、Mg2+、K+、Ga2+、SO42-、Cl-。因當?shù)貧夂蚋稍?，蒸發(fā)量大，引發(fā)地下水中鹽分向土壤表層遷移，

8、加劇了土壤鹽漬化程度。據(jù)研究，該區(qū)經(jīng)過3-5年的引水灌溉后，土壤表層就會產(chǎn)生積鹽現(xiàn)象。據(jù)內(nèi)蒙古自治區(qū)水利廳對河套灌區(qū)鹽分動態(tài)觀測資料分析，耕地潛水位上升10cm , 0-100 cm土層晝夜積鹽量達0. 0705-0 .1005t/hm2 ，鹽荒地可達0. 3000-0.4005 t/hm2。Topsoil salt mainly comes from underground water and bottom earth, therefore, the main factor that soil in this region becomes saline and alkaline is the

9、 rising of underground water level. From this aspect, the rising and lowering of underground water level is closely linked with irrigation. The study shows that underground water level in the irrigation phase rises by 0.85-1.32m, compared to that in non-irrigation phase, meanwhile, salt in the topso

10、il increases with the irrigation amount increasing. Because irrigating water in this region mostly comes from water in Huang He River, underground water has been ignored to be used ,which causes the rising of underground water level year in year. According to a recent study ,the bottom line of under

11、ground water level in this region should stand at 1.5-2.4m ,if water overpasses this line ,alkalinity and salinity in water are likely to occur, ,actually, underground water level rises to 2-5m at present, So salinity and alkality in underground water of this region distribute unevenly .Normally, th

12、e density of water is 10g/L,some of which is less than 1 g/L and water ions consist of Na+、Mg2+、K+、Ga2+、SO42-、Cl-。 Water evaporates quickly when its dry, which makes salinity in water will divert into topsoil, intensifying soil salinity. The study shows that salification on topsoil takes place when

13、irrigation has been carried out for three to five years. The study on soil salinity of irrigated area in He Tao conducted by Mongolian water conservancy bureau shows that underground water table has risen by 10cm,0-100 cm and soil salification at daytime and night has reached 0.0705-0 .1005t/hm2 ,sa

14、line waste lands 0. 3000-0.4005 t/hm2過量灌溉是該區(qū)耕地鹽堿化的最主要原因。過量灌溉會增加進入土地的鹽分，并提高地下水位，水隨鹽來，促進地表積鹽。黃河是中國的母親河，沖積平原適于原始農(nóng)牧業(yè)的發(fā)展，早在6000多年前，流域內(nèi)已開始出現(xiàn)農(nóng)事活動。戰(zhàn)國初期，黃 河流域開始出現(xiàn)大型引水灌溉工程。此后數(shù)千年，該地區(qū)的人們都開渠灌田，灌溉面積逐漸擴大。中華人民共和國成立后，該區(qū)發(fā)展進入新階段，土地開發(fā)強度逐漸增大，許多林地和草地也變成了灌溉農(nóng)田，至上世紀90年代末，共增加灌溉面積約200萬公頃。黃河上游是生態(tài)脆弱區(qū)，蒸發(fā)量大，隨著地表植被的破壞，最終導致了鹽堿化。近年來

15、，由于氣候的暖干化、水資源的短缺以及社會經(jīng)濟的迅速發(fā)展和人口增長對水的需求日益增加，黃河水資源供需矛盾不斷加劇，灌區(qū)引水量逐漸減少，加上灌區(qū)內(nèi)存在配套工程老化現(xiàn)象，灌溉面積有逐步萎縮的趨勢。這又意味著會有大量撂荒地出現(xiàn)，撂荒土地由于沒有灌溉排鹽和農(nóng)藝治鹽措施，土壤表層將會出現(xiàn)大量積鹽，生態(tài)系統(tǒng)得不到修復，最終將導致嚴重鹽堿化。The main reason for salinization and alkalization of farmlands is over-irrigation, which increases salinity of lands, lifts up undergrou

16、nd water level and accelerate the formation of topsoil salification. Reaches of the Yellow River, referred as “the mother river “,belong to a basin area which is good for the development of primitive agriculture and animal husbandry. As early as over 6000 years, farming production was engaged in the

17、 basin are and large irrigation projects began to be carried out in the early warring states period, since when people living in this area irrigated their farmlands .After the foundation of PRC in 1949,a new phase came into this area where many forests and grasslands were changed into farmlands with

18、 more lands reclaimed .By the end of the 1990s ,the total irrigated area was about 2 million hectares . The upper reaches area of Huang He River has been salinized and alkalized due to vegetation devastation and the fragility of local nature conditions. In recent years, dry and warm climate, deficie

19、ncy in water resources ,demands for water increased the contradiction between supply and demand of water resources in Huang He River with fast development of social economy and the growing of population ,therefore, irrigated area tends to be shrinking with irrigated water amount deceasing and irriga

20、ted equipment aging ,which means there are a number of waste lands to be uncultivated. The uncultivated waste lands will have a great deal of salification on their soil surface layers and be salinized seriously because salt in the soil surface layers isnt discharged by irrigation as well as no salin

21、ity control measures are not taken.該區(qū)灌溉每年平均引黃河水量約為150-180億m³，占據(jù)黃河徑流量的35%左右。該區(qū)所在生態(tài)需水量約為160億立方米，另外，黃河還要保證中下游用水，因此，該區(qū)引水量偏多，使上游地域引排水沒有達到平衡狀態(tài)，積鹽作用顯著，另外還造成了當?shù)厮亮魇?，河道淤積等情況。近年來，國家對此有了一定的研究和認識，加上黃河上游氣候暖干化，水量逐漸減少，國家開始降低上游灌區(qū)的引水定額，減少了15%左右 ，隨著灌溉水量的減少，當?shù)貞獙Υ胧┎蛔?，土壤積鹽有所增加，導致生態(tài)環(huán)境惡化，土地鹽堿化、沙化，植被覆蓋度降低，湖泊、沼澤面積大幅度減少

22、，土壤蓄水能力和含水量下降，而土壤蓄水能力和含水量下降又進一步促使環(huán)境惡化，土地鹽堿化、沙化，植被破壞，往往造成惡性循環(huán)。The volume of water diversion from Huang He River which is used to irrigate in this area averages 15-18 billion m³annually, taking up around 35% of volume of runoff.The volume of water that is needed in this area stands at 16 billion

23、cubic meters, which ,additionally , ensure to satisfy the need of people in middle and lower reaches of river, due to more volumes of water diversion in this area, the balance was changed, soil satification serious, soil and water lost heavily ,water bed blocked by silt. In recent years ,Chinese gov

24、ernment began to reduce 15 percent of the volume of water diversion in upper reaches of river .when the volume of water discharge was reduced ,salification in soil surface layers began to increase because strategies taken by local government to deal with these problems are insufficient ,which makes

25、environment degraded, land salinizing and desertifying, the vegetation coverage decreased, lake and marsh area substantially reduced , water holding capacity and moisture content in soil going down.該區(qū)灌溉水的利用效率較低，不但造成了灌溉水的浪費，且造成了該區(qū)整體空間水的過飽和，使地下水位居高不下，土壤積鹽嚴重。據(jù)研究，該區(qū)水資源利用系數(shù)僅0.3-0.45，綜合灌溉定額一般在4500-9000m³/hm²之間，河套灌區(qū)局部區(qū)域甚至高達9000-19500m³/hm²，而相關研究顯示，油葵灌溉1050 m³/hm²，玉米灌溉3150 m³/hm²時產(chǎn)量最高，該區(qū)灌溉定額過高，而適中的儲水灌溉定額，不僅有利于作物的生長，還有利于灌溉水分利用效率的提高。另外，據(jù)研究，該區(qū)若配合渠系防滲等工程措施，可使渠系水利用系數(shù)從055提高到08。Due to the lower efficiency of utilization of irrigated water