| Water is a key factor that restricts its ecosystems and ecological processes in aridand semi-arid areas. It is of great significance for the severe water shortage areas tostudy of hydrological processes and understand how water resources transformationaffects soil and vegetation. Water resources of Minqin oasis in the lower reaches ofthe Shiyang River are limited. It caused serious damage to the ecological environmentby unreasonable use of water in a long term. Micro runoff has been ignored and lackof researches in long term. As an integral part of the four-water transformation indesert, the micro runoff is a great value of eco-hydrological effects and ecologicalvegetation recovery. It is used by the principles of hydrology and as the researchobject of the oasis-desert transition zone of the northwestern edge of the dam area inMinqin oasis. Combined field observations with artificial simulation, the micro runoffhydrological processes were studied in Minqin oasis-desert transitional zone. Resultsare as follows:（1）Rainfall total change of from2006to2012was small, and in accordancewith the normal distribution; precipitation in Minqin oasis unevenly distributed, quitedifferent, the highest in July, the lowest in December; it was uneven seasonaldistribution, the precipitation of summer and fall accounted for78.45%, spring andwinter accounted for21.55%; Rainfall at night was more than day rainfall; theprecipitation of the Minqin oasis is mainly <5mm precipitation, accounted for about80%of the number of annual rainfall. With the series increased rainfall, rainfallfrequency decreased.（2）When it was heavy rain, micro runoff existed the surface of thecrust-covered sand dunes in the Minqin oasis-desert transitional zone. Based on thedifferent stages of the production, micro runoff could be divided into two parts of thecatchment areas and stagnant water areas. The runoff stage of catchment wasbelonging to slope runoff process.（3）Artificial simulations of micro runoff in the Minqin oasis-deserttransitional zone showed:at the same rainfall intensity, there was less time and morerunoff per unit area on physical crust. The time of runoff in fact was more thansimulation, which was due to that natural rainfall intensity was small at the beginningof the rain. There was the rainfall of33.6mm, the average rainfall intensity1.03mm· min-1at July29of2012. The time of runoff of physical crust was13.6min,and the lichen crust is15.2min. （4）In Minqin oasis-desert transitional zone micro runoff area, the depth ofwater infiltration increased with increasing rainfall intensity, which was the specificperformance: when rainfall intensity of33.6mm·d-1, soil moisture within30cmchanged apparently in24h, and within50cm starting to increase after24h; whenrainfall intensity2.2mm·d-1, only soil moisture within10cm changed; when rainfallintensity9.6mm·d-1, soil moisture within20cm changed apparently; at the samerainfall intensity, the infiltration rate of lichen crust was lower than physical crust inearly, but infiltration was more. In the case of no rainfall, soil moisture within10cmfluctuates in the24h. It declined from8:00to20:00, and rised from20:00to8:00thenext day. In192h, soil moisture within30cm fluctuated and the overall downwardtrended.（5）The stable infiltration rate q, moisture absorption rate S and hydraulicconductivity K of lichen crust and physical crust were measured in the negativehydraulic head （-3cm,-9cm,-15cm） with disc infiltrometer. At the same hydraulichead, q, S and K of lichen crust was much than the physical crust. With the increase ofthe negative hydraulic head, stable infiltration rate q, the moisture absorption rate of S,hydraulic conductivity K decreased. When removing the crust, infiltration rate q,moisture absorption rate of S, the hydraulic conductivity K had increased more than50%under the same hydraulic head, which showed that the presence of the crusthindered soil moisture infiltration. |
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