The measured data of precipitation for many years in 230 meteorological statiomshow that the mean annual precipitation is 492mm

in the Loess Plateauand about 52% of that is concentrated in summer. The annual prcipitation in theLoess Plateau is small

and its distribution is more centralized than that in the samelatitude regions. The precipitation has a distinct feature of level zone that reducesexponentially with inerease of latitude and increases gradually with increase of longitude. The mean level variation rates of annual precipitation are 60mm per latitide.and 26mm perlongitude. Within the different level zones

the less the precipitationis

the bigger the level varing rate of precipitation is

In respect to the verticaldistribution of precipitation

the relationship of the precipitation and elevtion is a parabola in the mountains

and the elevation of maximum annual precipitation is from 2300 meters to 2700 meters. The vertical increasing rate of precipitation is verydifference in the different mountains. As to the Loess Plateau

the relaionship of theprecipitation and elevation is negative correlation and the precipitation reduceswith the increase of the Elevation. that is lower than 1800 meters