专业英语翻译 求助!!!

麻烦各位大GG JJ 帮忙搞定这个啦! 我外语实在太烂~!!!
下面这一段:
One watershed where the water budget has been studied in detail is the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire . between 1956 and 1974 , annual precipitation averaged 1300 mm with 500 mm being returned to the atmosphere in evapotranspiration an 800 mm leaving the watershed as runoff in streams .
Over the period studied , there was considerable interannual variability in annual precipitation , which ranged from 950 mm to 1860 mm .Evapotranspiration remained relatively constant from year to year , ranging from 418 mm to 542 mm Evapotranspiration did not increase in wetter years or decrease in drier years .