太湖典型地区雨养麦田的径流发生时间特征

明确农田径流发生的时间特征对因时因地制定径流养分削减策略具有重要意义。本文基于太湖流域典型地区(苏州、无锡、溧阳、湖州)60 a历史降水时序变化和12 a正常气象年份田间径流实际发生的时间特征,分析了太湖流域雨养麦田的径流发生时间特征。结果表明,太湖地区年均降水量和小麦生长季均值降水量分别为1 164.8 mm(657.7~1 643.7 mm)和514.6 mm(207.3~742.8 mm)。除个别年份,年降水距平百分率基本在±25%左右变化(正常)。剔除偏涝年和偏旱年后的小麦生长季降水概率和日均降水量月度时序变化均表现为先下降后升高的趋势,12月降水概率和日均降水量均最低。从小麦生长季12 a径流发生时间统计结果来看,2月(19.05%)和3月(18.10%)径流发生次数占比较高,12月(16.19%)、4月(13.33%)和5月(15.24%)径流发生次数的占比相当。不同年份驱动径流发生的实际最小降水量为8.1~19.4 mm,径流发生概率与降水发生概率变化并不完全一致。结果表明,太湖地区雨养麦田驱动径流发生的最小降水量范围为8.1~19.4 mm,2月和3月是径流发生的高风险期,12月、4月和5月是次高风险期,径流发生概率与降水发生概率变化并不完全一致。

Temporal characteristics of runoff-occurrence in rain-fed wheat fields in typical areas of the Tai-lake region, China

It is important to clarify the characteristics of farmland-runoff to develop a nutrient reduction strategy based on temporal and spatial characteristics. Based on variations in the 60-year historical precipitation sequence and the occurrence of actual field-runoff in the typical area of the Tai-lake basin, this paper analyzes the characteristics of runoff occurring from rain-fed wheat fields. The results showed that in the Tai-lake basin, the annual average rainfall and that during the wheat-growing season were 1 164.8657.7, 1 643.7] mm and 514.6 mm207.3, 742.8] mm, respectively. Except for a few years, the annual precipitation anomaly percentage usually changes by ±25% (common). After excluding flood and drought years, the monthly time series of precipitation-probability and daily-precipitation during the wheat growing season, showed a trend of first decreasing and then increasing. The precipitation probability and average daily-precipitation were lowest during December. Based on the statistical results of runoff occurrences during the wheat-growing season over 12 years, the number of runoff occurrences in February (19.05%)and March (18.10%)was relatively high. The proportions of runoff occurrences were approximately equivalent in December (16.19%), April (13.33%), and May (15.24%). The actual range of the minimum precipitation that drives the runoff was 8.1 to 19.4 mm. The results show that the range of the minimum precipitation in rain-fed wheat fields that drives runoff in the Taihu lake region is 8.1 to 19.4 mm. The probability of runoff occurrence in rain-fed wheat fields in the Tai-lake region is not completely consistent with that of precipitation. The months of February and March are the first high-risk runoff periods; December, April, and May are the second-high risk periods.