To better understand the characteristics of soil water cycle in the semi-arid Loess Hilly Ｒegion and to provide
background data for the change in land cover，a typical sloping filed which was abandoned for many years was selected at
the Shanghuang Experimental Station in southern Ningxia． Dynamics of the soil water were continuously monitored by using
a neutron probe in fixed positions． The results showed that the rainfall was not frequent and precipitation was limited． The
amount of rainfall recharge ( y) was positively correlated to the precipitation ( x) ，as expressed in the equation y = 0． 44x
－ 0． 58 ( Ｒ2 = 0． 980，P ＜ 0． 01) ． The recharge coefficient was 0． 44，and the rate of rainwater harvesting was to be
improved． Similarly，the recharge depths were increased with the precipitation． The impact of rainfall on soil water content
was mainly concentrated to the top 40 cm of the soil． There was a time lag between the rainfall recharge and the soil water
in deeper soil layers． The soil depths could be effectively recharged by rainfall of more than 50% precipitation events in a
whole year were defined as the general infiltration depth． This concept was helpful to redefine assessment standards of dried
soil layer ( DSL) ． In the study area，the general infiltration depth was 0—40 cm． Although continual rainfall increased the
movement of soil water to deeper soil layers，the maximum infiltration depth did not exceed 300 cm during the observation
period． Meanwhile，evapotranspiration in this region was always positively correlated to air temperature and soil watercontent． During the growing season，evapotranspiration was stronger than in the non-growing season and it was higher in the
wet year and lower in the dry year than in the year with normal level of precipitation． Soil water content，which was
influenced by evapotranspiration，decreased with soil profile． The major depth that was affected by evapotranspiration was
0—200 cm，with the maximum depth reaching to more than 300 cm． Furthermore，seasonal changes in the soil water
storage showed a V-shaped trend，with the minimal value appearing at June or July． The average soil water content in the
soil profile showed a reversed S-shaped trend，with the maximum and minimum values at the depth of 40 and 200 cm，
respectively． Additionally，variance coefficient of the soil water from the soil profile showed a decreasing power function
trend with the increase of soil depth． Ｒeferring to the results of vertical division of soil water profiles by the sequential
clustering method，the variance coefficient of 0． 20 and 0． 05 could be used as criterions to divide the soil water profile into
three levels: the active layer ( 0—40 cm) ，the second active layer ( 40—200 cm) ，and the relatively stable layer ( deeper
than 200 cm) ． In the wet year，due to continual rainfall infiltration and strong evapotranspiration，the variance coefficients
at the soil depth of 0—200cm were increased and the range of active layer was broadened．
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