降雨侵蚀力是进行土壤流失量预报的基本因子,EI30是迄今得到广泛应用的定量指标,但它的计算需要降雨过程资料,使其推广应用受到很大限制。用自动气象观测提供的高精度等间隔降雨资料,代替降雨过程资料,是估算降雨侵蚀力指标的首选。国际上对此已有研究,发现有很大的地区差异性。为此,本文在水蚀严重的中国东部季风区选择5个代表站点,共456次降雨过程资料,建立了用60 min等间隔雨量资料估算次降雨侵蚀力的计算方法。研究结果表明:直接用60 min等间隔资料计算的降雨侵蚀力指标值,与用降雨过程资料计算的结果相比,降雨动能E差异较小,主要差异体现在最大30 min雨强I30上,由此导致降雨侵蚀力指标EI30的差异也十分明显。利用自动气象观测小时雨量资料计算降雨侵蚀力指标值,通过公式(EI30)bp=1.730(EI30)60转换,可以较精确地估算全国降雨侵蚀力,与用日、月和年降雨量资料的估算值相比,能够提高土壤侵蚀预报精度。
Rainfall erosivity shows the potential ability of the soil loss caused by rainfall and it is a very important factor for predicting soil loss from agricultural hillslopes. EI30 is a widely used index for quantifying rainfall erosivity. The 'E' portion of this value represents the rainfall energy, and the 'I30' portion represents the maximum, contiguous 30-minute rainfall intensity during the storm. Normally, EI30 values are calculated from breakpoint rainfall information taken from continuous recording rain gauge charts, however, in many places in China the detailed chart-recorded rain gauge data relative to storm intensities are not readily available. Obviously, the more detail of the rainfall data was used, the more accurate of EI values were given. In order to take advantage of hourly rainfall data in automatic meteorological observation stations and improve the precision of EI values. A total of 456 storm events in 5 soil conservation stations over eastern China were used to determine if EI values could be calculated by using hourly rainfall data (60-min interval data). Results indicated that the values of EI30 based on the 60 min interval data were less than those calculated from breakpoint data. The average conversion factors (ratio of values calculated from the breakpoint data to those from 60 min interval data) for the five stations are 1.105 for the estimation of E values, 1.668 for I30 values, and 1.730 for EI30 values. The differences between two kinds of EI values based on breakpoint data and hourly rainfall data are mainly caused by maximum 30-min rainfall intensity. Hourly rainfall data can be used to accurately determine the rainfall erosion index values by using this function:(EI30)bp=1.730(EI30)60.The result could be used to improve the estimation of rainfall erosivity indices, and hence prediction of soil erosion in China.
[1] Wischmeier W H, Smith D D.Rainfall energy and its relationship to soil loss.Transactions, American Geophysical Union, 1958,39:285~291.
[2] Wischmeier W H.A rainfall erosion index for a universal soil loss equation.Soil Science Society Proceedings,1959,23(3):246~249.
[3] Wischmeier W H, Smith D D.Predicting rainfall erosion losses: A guide to conservation planning.U.S.Dep. Agric. , Agric. Handb. , No.537,1978.
[4] Renard K G, Foster G R, Weesies G A,et al.Predicting Soil Erosion By Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation(RUSLE).U.S. Dep. Agric. , Agric. Handb. 703, 1997.
[5] Sharpley A N, Williams J R.EPIC—Erosion/Productivity Impact Calculator.U.S. Department of Agriculture Technical Bulletin,No.1768, 1990.
[6] 黄炎和,卢程隆,郑添发,等.闽东南降雨侵蚀力指标R值的研究.水土保持学报,1992,6(4):1~5.
[7] 周伏建,陈明华,等.福建省降雨侵蚀力指标R值.水土保持学报,1995,9(1):13~18.
[8] 吴素业.安徽大别山区降雨侵蚀力简易算法与时空分布规律研究.中国水土保持,1994,4:12~13.
[9] 张宪奎,许谨华,卢秀琴,等.黑龙江省土壤流失方程的研究.水土保持通报,1992,12(4):1~9.
[10] 杨子生.滇东北山区坡耕地土壤流失方程研究.水土保持通报,1999,19(1):1~9.
[11] 赵富海,赵宏夫.编制张家口市降雨侵蚀力R值图的研究.见:永定河上游张家口市水土流失规律与土地改良利用.北京:环境科学出版社,1995.16~22.
[12] 王万忠.黄土地区降雨侵蚀力R指标的研究.中国水土保持,1987,(12):34~40.
[13] 贾志军,王小平,李俊义.晋西黄土丘陵沟壑区降雨侵蚀力指标R值的确定.中国水土保持,1987,(6):18~20.
[14] 江忠善,李秀英.黄土高原土壤流失方程中降雨侵蚀力和地形因子的研究.中国科学院西北水土保持研究所集刊,1988,7:40~45.
[15] 王万忠,焦菊英.中国的土壤侵蚀因子定量评价研究.水土保持通报,1996,16(5):1~20.
[16] Arnoldus H M J.Methodology used to determine the maximum potential average annual soil loss due to sheet and rill erosion in Morocco.FAO Soil Bulletin,1977,34:39~51.
[17] Richardson C W, Foster G R, Wright D A.Estimation of erosion index from daily rainfall amount.Transactions of the ASAE,1983,26(1):153~156.
[18] Lo A, EI-Swaify S A, Dangler E W, et al.Effectiveness of EI30 as an erosivity index in Hawaii soil erosion and conservation.Soil Conservation Society of America, Ankeny. 1985. 384~392.
[19] Ferro V, Giordano G, Iovino M.Isoerosivity and erosion risk map for Sicily.Hydrol. Sci. J. , 1991, 36(6):549~564.
[20] Renard K G, Freimund J R.Using monthly precipitation data to estimate the R-factor in the Revised USLE. Journal of Hydrology,1994,157:287~306.
[21] Yu B, Rosewell C J.An assessment of a daily rainfall erosivity model for New South Wales.Australian Journal of Soil Research,1996,34:139~152.
[22] Yu B, Rosewell C J.A robust estimatior of the R-factor for the universal soil loss equation.Transactions of the ASAE,1996,39(2):559~561.
[23] Yu B.Rainfall erosivity and its estimation for Australia's tropics.Australian Journal of Soil Research, 1998, 36(1):143~165.
[24] 孙保平,等. USLE在西吉县黄土丘陵沟壑区的应用.西北水土保持研究所集刊,1990(12):50~103.
[25] 刘秉正.渭北地区R的计算与分布.西北林学院学报,1993,(2):21~29.
[26] 马志尊.应用卫星影像估算通用土壤流失方程各因子值方法的探讨.中国水土保持,1989,(3):24~27.
[27] 谢云,章文波,刘宝元.用日雨量和雨强计算降雨侵蚀力.水土保持通报,2001,21(6):53~56.
[28] 章文波,谢云,刘宝元.利用日雨量计算降雨侵蚀力的方法研究.地理科学,2002,22(6):706~711.
[29] 章文波,付金生.不同类型雨量资料估算降雨侵蚀力.资源科学,2003,25(1):35~41.
[30] 章文波,谢云,刘宝元.用雨量和雨强计算次降雨侵蚀力.地理研究,2002,21(3):384~390.
[31] Weiss L L.Ratio of true to fixed-interval maximum rainfall.Journal of the Hydraulics Division,ASCE, 1964,90(1): 77~82.
[32] Istok J D, McCool D K.Effect of rainfall measurement interval on EI calculation.Transactions of the ASAE,1986,29(3):730~734.
[33] Christopher Daly, George H Taylor.Development of New Spatial Grids of R-factor and 10-yr EI30 for the Conterminous United States.The U.S. Environmental Protection Agency (EPA), Las Vegas:NV.2002.
[34] Williams R G, Sheridan J M.Effect of measurement time and depth resolution on EI calculation.Transactions of the ASAE,1991,34(2):402~405.
[35] Brown L C, G R Foster. Storm erosivity using idealized intensity distribution. Transactions of the ASAE,1987,30:379~386.
[36] 袁志发,周静芋.试验设计与分析.北京:高等教育出版社,2000.165~171.
