祁连山水源涵养文章a study on water conservation in qilian mountains area of china

1、A study on water conservation in Qilian Mountains area of China: A reviewAbstract: Water conservation is one key ecological function of forests espelly inthe upper reaches of rivers and streams. From the aspect of hydrological proses,water conservation can be groupedo three servi: rainfallerception,

2、 soil waterstorage and fresh watrovi. As Qilian Mountains was the birthplace of severalinland rivers (Heihe River, ShiRiver, Shule River, etc.) for the existing of glalregion and precipiion, it isthe most important green shelter in the arid andsemi-arid western China, raising the Hexi corridor and S

3、ilk Road. To monitor the function of water conservation in Qilian Mountains area and assess the potential storage increasement are of great significance for the health of the ecological and economic development of the arid and semi-arid basins of Hexi corridor inland waters, the Qaidam inland waters

4、 and Hala lake inland waters. Many scientists have doneresearches in the Qilian Mountains area espelly in the recent ten years, andresearchcontentscovertheprosmechanismofhydrologicalresponses,afforesion and environmental efficiency as well as economic compensation, mand GIS application, glacier chan

5、ges, relationship betn water conservation andurbanization, etc. This pr has given a summary of these researches,yzed themeaning of them, and prospected the future research in the Qilian Mountains areaegrating theernational forefront studies and hot ies.Key words: water conservation; hydrological res

6、ponse; glacier; afforesion; m and GIS application; Qilian Mountains1roductionThe definition of water conservation is usually connected with water reduction according to the Wikipedia, but we focus on water conservation of forests in thispr.he past years, watershed or watershed protection forest (Chi

7、na agriculturalencyclopedia), water-source containing forest (Dictionary of agriculture), forest forconservationofwatersupply(Chi-EnglishDictionaryofagriculturalclassifications) and other similar words and phrases are used in China to describe this subject. Forests and water are important material b

8、asis for human existence anddevelopment (et al., 2001). The former is the main subjects of terrestrialecosystems, and the latter is the main carrier of matter circulating and energy flow of ecosystem (Jiang et al., 2006). As a key ecological function of forests (regulating slope and underground runo

9、ff, reducing the amount of sediment, soil and waterretention, flood detention and storage, water regulation, waturification, climateregulation, wildlife conservation, etc.), water conservation can be groupedo threeproses: rainfallerception, soil water storage and fresh watrovifrom theaspect of hydro

10、logical proses.Qilian Mountains (9925- 10328E, 3645- 3936N) locatedhenorth-east of Qinghai province and west edge of Gansu province, comed of severalnorthwest southeast direction parallel mountains and wide valleys, and the west end connected to Aerjin mountain while the east end connected to Qinlin

11、g Mountains, stretching for almost 1000 kilometers, while the mountains elevation are mostlybetn 4000 to 5000 meters. The mountain peaks over 4000 meters high are coveredwith snow all the year. As den the northwest of China, Qilian Mountains have thecharacteristics of typical continental climate, an

12、nual precipi ion ranges from 150 mm to 800 mm and annual average temperature ranges from 6 to -5 as the elevation rising, and the vertical vege ion distribution is obvious but differed from east part to west part of the mountains, so does on the southern slopes and northern slopes of mountains. Vert

13、ical vege ion belt on the northern slope in the easternsection (bottom up): desert belt mountaeadow belt mountain forest andmeadow belt alpine shrub and meadow belt alpine sub-i parse vege ion belt; South slope: meadow belt mountain forest and meadow belt alpine shrub and meadow belt alpine sub-ice

14、sparse vege ion belt. Northern slope of the west section (bottom up): desert belt mountain meadow belt alpine meadow belt alpine sub-i parse vege ion belt; South slope: desert belt alpine meadow belt alpine sub-ice sparse vege ion belt (Xu et al., 2006). The distribution of water conservation forest

15、s in Qilian Mountains account for 6 forest stands of wet shrub forest，moss-Picea crassifolia forest，shrub-Picea crassifolia forest，grass-Piceacrassifolia forest，Juniperus przewalskii forest and dry shrub forest (Zhang et al.,2007). The water storage capacity of forestshe Qilian Mountains was account

16、ed to552 million cubic meters according to the calculation of Che et al. (1992).Under the influence of Pacific monsoon and the water increasing effect of mountains（Ding et al., 2003; Wu et al., 2005）, the east part of Qilian Mountains islike a wet islandhe arid region of northwest China. Without Qil

17、ian Mountains, thedeserts in Inner Mongolia and Qaidam maybe blendo each other, and then thedeserts may push significantly to the direction of Lanzhou. Withoutthe Qilian ve been so l locationMountains and the glaciers and huge precipiion on it, there would nomany rivers, also would nove Hexi corrido

18、r the Silk Road. The speand typical vege ion distribution makes the water conservation function of Qilian Mountains extremely huge and important. Many scientists have done researches in Qilian Mountains on different subjects.Review and summary of previous studiesHydrological response of forestsThe w

19、ater conservation pros of forest can be dividedo four components: canopyerception, stem flow, water transport and storage in ground litter, water transportand storage underground. Canopy is the ecosystem, and it has great impact on theerface of water transporthe forestwater transport of othererfa. T

20、hesignificance of ground litter is not only on the aspects of water retention andconservation, but alsos on the impact of soil water transport and circulation, aswell as the improvement of soil properties.Canopyerception is closely related to precipiion, forest structure, plant species,forest covera

21、ge, etc. (Liu and Lu, 1996; Cui and Bian, 1980; Liu et al., 1987; Wen and Liu, 1995), Dang et al. (2004) have done researches on this subject in Qilian Mountains, andyzed the water retention capacity of different canopy density of Qinghai spruce, mountain shrub, wild grass. Many scientists also calc

22、ulated the erception rate of different species of plants (Wang, 2000; Peng, 2010; Hu et al., 2004; Dang et al., 2004). As the main constructive species, Qinghai spruce (Picea crassifolia) and Qilian juniper (Juniperus przewalskii) were studied the most (Jin et al., 2001; Tian et al., 2011; Tan et al

23、., 2009; Qin et al., 2007; Dang et al., 2004; Sun et al.,2010). Tian et al. (2011) simulated the evopotransperation of Qinghai spruce forestin the Qilian Mountains, and foundt canopyerception evaporation couldincrease rainfall and moren one-quarter of the total rainfall was directlyevaporated back t

24、o the atmosphere by canopyhe Qinghai spruce forest. Tan et al.(2009) studied theerception feature of Qinghai spruce based on different canopyclosure and rainfallensity. About 10-40% of total rainfall or snowfall will beercepted by forestry canopy according to the previous researches (Jin et al., 200

25、1),though anerception rate as high as 66.5% was measuredhe shrubs (Chang et al.,2002). Of course, under different site conditions the evaporation rate would be different as the rainfall, temperature and solar radiations being widely different. Alsoevenhe same forest, there are seasonal differenfor e

26、vapotranspiration.Stemflow refers to the part of rainfallt passed by the leaves and along the treetrunk after canopyerception, then finally reaches to the ground. Some timesstemflow is considered to be an important component of canopy erception. Chang et al. (2002) found t only when the rainfall exc

27、eeds 12mm stemflow could be happen in the Qinghai spruce forests, and it only account for 0.51% of the rainfall. Although it is usually a small value in calculation of water balance and so on, it canreduce the eroof raindrop, and bring along the nutrients from the canopy directlyo the soil around fo

28、rest trees rhizosphere, promoting forest water and nutrients accumulation (Zhou et al., 2004; Wang, 2000).Ground litters have diversified forms of eco-hydrological effects including waterretention, ground flow, evaporation restra, corropreventing,increasing soilanic matter, improving soil structure

29、and properties, etc. (Chang etal., 2001; Chang et al., 2002; Sun et al., 2010; Dang et al., 2004) Leaves are the main components of ground litters, so the capacities of water conservation vary grey in different kind of forests as the physiological traits are different betn tree species. he previous

30、studies, ground litters of Moss spruce forests, Shrub spruce forests, Young spruce forests, Qilian juniper forests and Sub-alpine shrub have been studiedthe most, covering the indicators of average thickness, storage,al waterholding rates,um water capacity, etc. (Dang et al., 2004). Usually, the mos

31、sspruce forests have a better ability of water retention. It should be notedt thes of different scientists were not always consistent, for the canopy coverage and sites conditions were not the same in their experiments. As the temperature of growth environments of Alpine shrubs and Subalpine shrubs

32、are lower compares toConiferous and Broad-leaved forests, the littosition rates of Alpine shrubsand Subalpine forests are the slowest, resulting the greatest water retention rate(Chang et al., 2001); the Broad-leaves forests distributedhe low elevation areasand grow fast, but when the canopy closure

33、 rate reached a high level, the growing conditions of the trees would decline and resulting the lowest water retention rate of litter (Xu et al., 1984). According to Sun et al. (2010), the soil water retention rate of litters is in the following order: Alpine shrubs Qinghai spruce Qilian juniper Slo

34、pasture. But as existing storage of the litters vary grey, though the Alpineshrubs have the highest water retention rate, usually the Qinghai spruce forests havethe greatest water storage. Theum water holding capacity of Mass-spruceforest could reach as high as 124.98t/hm2 according to Chang et al.

35、(2001). Theeffects of runoff reduction and eroprevention of litter are significant. If the litteris removedhe Qinghai spruce forest, the runoff will increase 180% and the eroincrease 787% (Chang et al., 2001).Permeability is the basal factor influencing the ability of water conservation of soil, and

36、 is closely related with soil porosity, which is including the total porosity, non-capillary porosity and capillary porosity, etc. (Ding et al., 2010; Sun et al., 2010; Qin et al., 2007a). Soil porosity is gre y affected by plant species, many scientists have done researched on soil porosity of diff

37、erent plants (Qin et al., 2010b; Dang et al., 2004; Niu et al., 2001; Dang et al., 2006). Although the water storage is gre y affected by forest planting density, forest age, slope degree, etc. (Hu et al., 2004; Qin et al., 2007b), usually within soil thick in 1 meter, moss-spruce forest, shrub-spru

38、ceforest, alpine shrub forest and the Chipine (Pinus Sinensiswhile) foresvelarger water storage capacity compared to Qilian juniper (Qin et al., 2010b; Ding et al., 2010). But on the comparison of Shrubs, coniferous and broadleaved forests, the soil water capacity is in the following order: Shrubs c

39、oniferous forests broadleaved forests (Qin et al., 2007).Contrastive studies on the water conservation ability of different vege ion types and coverage rates have been done by many researchers in recent years (Dang et al., 2004; Miao et al., 2006). Mountain woodland and grassland are covered with di

40、fferent degrees of bryophytes and litter layer, and always with a thick humus layer, whichmaking it easier for mountain woodland and grassland to store precipi al., 2003b). The steady annual accumulation of litter and lowion (Song et ition ratecausing by the relatively lower temperaturehe forest mak

41、e the forestse thetypical and greatest water conservation body, and the soil water retention capacity offorests is also greatern slope pasture (Zhang et al., 2007). The influence of forestcoverage rate on surface runoff is also significant.he dry or wet years, streamflowof the rivers with high fores

42、t coverage rate change small and nearly the yield of normal year (Miao et al., 2006). The regulating effect of forest to the seasonalvariation offlow and river runoff is significant (Miao et al., 2006), espellythe flood preventionhe rainy season.2.2 Mand GIS applicationMand GIS was widely used in wa

43、ter conservation researches at catent andregional scale. Three general methods are available on water conservation researches.One method is watershed experiments, another is time seriesysis based oncharacteristic variables (Conway, 2001), and the third one is mapproach (Chen etal., 2004a). From theo

44、f m-building, there are two formats ofhydrological m, lumped hydrological mand distributed hydrological m(Michael et al., 1996; Yuan, 1990; Wang et al., 2003b; Xie et al., 2007). From themethod of m-building, mapproach can be classified as physical mingmethod and mathematical ming method (Liu et al.

45、, 1996; Michael et al., 1996).Distributed ms are the most widely used maccording to our searchingrecords (Abbott and Bathurst, 1986; Bathhurst et al., 1995; Wang et al., 2003b). Asone of the distributed m, SWAT (Soil and Water Assessment Tool) has beensucsfully usedhe Heihe river basin (Wang et al.,

46、 2003a), Shiriver basin(Wang et al., 2010a) etc., and it could reflect the ecological effect of vegeion coverson hydrological response (Wang et al., 2010a).Since the SWAT mneedty and long-time series of data (DEM, Land-use, Soil property, Meteorologicaldata, etc.) as the basic material forysis, the

47、final results of ming were usuallynot perfect because of the data limiion. SCS (Soil Conservation Service) mproed by U.S. Soil and Water Conservation Bureau is one of the extensivelyappd hydrological ms which are mathematical ms established on thesimulation of watershed hydrological pros. Compared t

48、o SWAT m, SCS mhas the characteristic of simplicity, loose requirements on parameters and observation datasets (Liu et al., 2010). Through the study of the water conservation of QilianMountains based on surface energy balance and SCS m, Nie (2010) offered apractical method forive evaluation of regio

49、nal water conservation using thismethod and GIS software as a platform. Rainfall and evaporation data, surface runoff data, TM and ETM salite data, DEM data were used in his research. Although thereare differenbetn calculated values and actual values, the SCS mbased onsurface energy balance can be c

50、onsidered as an effective method of water conservation research.He et al. (2012) using the formula of water balance m ed the water balance, assessed the contribution of different vege ion types to annual water yield, and studied the relationship bet n forests and annual water yield in a small cat en

51、t named Pilugou in the Qilian Mountains. Picea crassifolia is a main species of the forests in Qilian Mountains and covered 38.5% of the cat ent area, but they found it contributed little to annual water yield. As forest may decrease the downstreamwater supply, they suggestedt forest cover should ha

52、ve an appropriate regionallevel.et al. (2005) did research on the relationship betn vegeion and waterbudgets using GIS and 15 years (1987-2001) of hydrological data in Dayekou and Haichaoba catents on Qilian Mountains. With the use of Landsat ETM+ (1:50000)and topography maps (1:50000) they foundt t

53、he main landscelementsaffecting hydrological proses were different. Grassland and Qinghai spruce (Piceacrassifolia) forest in the lower areas in Dayekou have the most closely relationship with water budgets but in Haichaoba they were shrubland and barren land in thehigher areas.Evapotranspiration is

54、 an important component in the equation of water balance,energy balance, mapplication etc. A modied Penmane Monteith equation wasused to simulate canopy transpiration and soil evaporation by Tian et al. (2011). Themed evapotranspiration (ET) of the Qinghai spruce foresthe study area for the2008 grow

55、ing season is 313.6mm, being acceptably consistent with the directlymeasured ET (298.2mm) by eddy covarianystem.The simulation or estimation of the glacier runoff pros in hydrological ms or massland surface ms is still limited (Zhang et al., 2012b).he estimation ofbalance (Water equivalent mass bala

56、nce, glacier mass balance, etc.)lacier runoff, temperature-index ms are often used and is considered to outperform theenergy-balance mespellyhe application of remote high-mountain regionsbecauseoftheirgenerallygoodperformance,lowdatarequirementsandcompuional simplicity on a catent scale (Zhang et al

57、., 2006; Zhang et al.,2012b). Zhang et al. (2012a; 2012b) describes a monthly degree-day mcoupledwireavolume scaling flacier melting. And with meteorological data (monthlyprecipiion and monthly temperature),t mcan be used to estimaong-termchanges in glacier area, mass balance and melt water. An appl

58、ication has been done in two watersheds of Yarkant River Basin and the Beida River Basin on their mvalidation, and the mis wellyzed the glacier ablation betn 1961-2006caused by increasing summer air temperature.Except for ms, tree-rings are used to reconstruct the past streamflow. Yin et al.(2008) p

59、erformed water balance ming using 1955-2002 meteorological data toevaluate the impact of the combined effects of temperature and precipiion changesover time, and foundt tree-ring widths were strongly correlated with variablesrepresenting soil moisture conditions obtained from the water balance m.Tre

60、e-ring chronologies explained up to 80% of the variation in the soil moisturevariablesheir regresysis, and the reconstruction of long-time soil moistureconditions (556AD-2001) revealed the major dry and wet periods. Then Qin et al. (2010a) did researches based on a well-replicated Qilian juniper rin