环洞庭湖丘岗地区雨水资源和管理策略

环洞庭湖丘岗地区是我国南方丘陵农林复合生态系统的典型板块。雨水资源对生态系统水环境、水平衡具有不可替代性。生态系统水环境要素的定位观测和小流域水平衡监测研究表明:该地区雨水资源呈季节性配置,系统水平衡过程有明显盈(季节性水富余311.3mm)、亏(季节性水亏缺134.7mm)现象。本地区自然降雨大约有76%产生派生资源参与系统水分循环,其余部分主要以径流形式溢泄入下游水域;雨水侵蚀使该地区每年流失或向洞庭湖水域输送水1.31×1010m3、泥沙1.64×106m3、养分(N、P、K)0.89×104t。集雨利用是本地区农业雨水管理的基本形式,据研究估测,可利用的集雨水量为现今农业可用地灌溉水需求量的2.41倍;可集雨水量和农业集雨需求量的比值与系统尺度有关。影响生态系统水平衡和农业集雨利用有两大因子,即人工蓄调雨水的局限性和坡地生态系统构建。因此,雨水资源的生态管理重在坡地系统构建---地表植被植物群落的组配和土壤生产力持续性保护。     

云南哀牢山大气降雨过程中养分输入及输出变化的初步研究

本文以滇西南中山湿性常绿阔叶林为研究对象,分析了大气降雨对该森林生态系统养分输入和输出的影响。结果表明,该地区在大气降雨过程中养分输入：Ｎ以大气降雨为主；Ｐ、Ｋ、Ｍｇ以穿透雨为主,它们分别占总输入量的６９．８５％、７７．３３％、９８．１９％和８０．４０％；Ｃａ养分输入,大气降雨和穿透雨约各占总输入量的一半,分别是４５．３５％和５４．３８％。养分输出以地下土壤渗漏为主,Ｎ、Ｐ、Ｋ、Ｃａ、Ｍｇ分别占总输出量的９６．５２％、８６．７９％、６９．１３％、９８．１７％和９７．２１％。在养分循环中Ｎ、Ｐ、Ｋ、Ｃａ分别增加了１５．９４１ｋｇ／ｈａ．ａ、０．３５３ｋｇ／ｈａ,ａ、３．８３ｋｇ／ｈａ．ａ和１．２６４ｋｇ／ｈａ．ａ．,而Ｍｇ则减少了０．６５４ｋｇ／ｈａ．ａ。     

CHARACTERISTICS AND CONTRIBUTING CAUSES OF AN ABNORMAL FREQUENCY OF FLOOD-PRODUCING RAINSTORMS AT CHICAGO1

ABSTRACT: Major hydrometeorological factors pertinent to defining and understanding the hydrologic characteristics of urban and other small-basin storms were investigated using data from a continuous 44-year operation of a recording raingage network in Chicago. Factors included: the frequency distribution of basin mean rainfall and its relation to storm maximum precipitation; the spatial distribution characteristics of each storm, including storm rainfall reduction factors which are widely used in hydrologic design problems; and weather-related causes related to the frequency and intensity of severe rainstorms in the Chicago area in recent years. Results have indicated that urban mean rainfall frequencies were overestimated in earlier studies in which they were derived from point/areal mean rainfall ratios obtained from much shorter records on rural networks. Reduction factors were found to vary between urban and rural storm systems due to urban-related effects. Two factors were found to be potential contributors to the characteristics of severe rainstorm occurrences at Chicago. These include urban-induced rain enhancement and an upward climatic trend in the occurrence of heavy rainfall events during the sampling period. Study results should be generally applicable to other large urban areas in the Midwest and other regions of similar precipitation climate.     

CALIBRATION OF SNYDER COEFFICIENTS FOR PENNSYLVANIA1

ABSTRACT Unit hydrograph theory is one of the most widely used techniques to predict surface runoff. The present study is concerned with the Snyder unit hydrograph and the calibration of the Snyder coefficients for Pennsylvania. Twenty-seven study basins were selected, located randomly across the state. With the rainfall and runoff recorded for several events for each basin (more than 500 events were analyzed) unit hydrographs were calculated and the Snyder coefficients determined. A map of the coefficients was drawn to illustrate the variability in the coefficients and two equations using multiple regression theory were developed. The unexplained variability of the coefficients suggests that upper and lower bounds on the peak flow might be placed on storm hydrographs developed for ungaged watersheds.     

ESTIMATING RUNOFF VOLUMES FROM URBAN AREAS1

ABSTRACT: Estimations of runoff volumes from urban areas can be made by the equation Q = a A σ(P_e– b), where Q is the runoff volume, a is the part of the total area A Contributing to runoff, P_e is the rainfall amount for a single event, and b is the initial rainfall losses. For the evaluation of a and b, rainfall/runoff measurements were made in five areas of sizes between 0.035 km² and 1.450 km². By linear regression analysis of rainfall volumes versus runoff volumes, the initial rainfall losses were found to vary from 0.38 mm to 0.70 mm for the different areas. The parts of the areas contributing to runoff were found to be proportional to the impermeable parts of the mas. The equation is applicable in urban areas with well defined paved surfaces and roofs and with a negligible amount of runoff from permeable areas.     

APPLICATION OF SCS INFILTRATION MODEL1

ABSTRACT: The SCS infiltration model was applied to the Ralston Creek watershed in eastern Iowa. The criteria to determine the various model parameters were revised to obtain a better agreement between the observed and computed total runoffs. A procedure to calibrate the infiltration model is presented. The infiltration model was used in conjunction with an overland flow model to develop flood hydrographs. The results indicate that SCS infiltration model adequately describe the distribution of losses.     

PREDICTING PEAK STREAM FLOW FROM AN UNDISTURBED WATERSHED IN THE CENTRAL APPALACHIANS1

ABSTRACT: Data from a small forested catchment were used to model peak stream flow as a function of basic hydrologic variables associated with 112 rain storms. Rainfall depth and initial stream flow rate accounted for 87.1 percent of peak flow variability. Forty expressions of rainfall intensity (describing both the temporal sequence of intensity for 20 equal storm intervals, and maximum intensity for 20 separate interval lengths) were used in an attempt to improve the predictability of basic models. None of the intensity parameters improved predictability by as much as 2 percent, apparently because the most intense rainfall bursts generally occurred near the beginning of storm periods. Mean rainfall intensity for entire storms was generally as effective as any of the shorter interval intensities, and its use helped to linearize the relationship between peak flow and rainfall depth and duration.     

EXPERIMENTAL MARVIN WINDSHIELD EFFECTS ON PRECIPITATION RECORDS IN LEADVILLE,COLORADO1

ABSTRACT: An evaluation of the Leadville, Colorado, precipitation records that include a reported record-breaking storm (and flood) at higher elevations in the Rocky Mountains has indicated that the use of an experimental Marvin windshield (designed to decrease the effects of wind on precipitation-gage catchment of snow during winter) resulted in substantially overregistered summer precipitation for 1919 to 1938. The July monthly precipitation for these years was over-registered by an average of 157 percent of the long-term July monthly precipitation at Leadville. The cause of the overregistration of precipitation was the almost 4-foot-top-diameter cone-shaped windshield that had the effect of “funneling” hail and rain splash into the rain gage. Other nearby precipitation gages, which did not use this Marvin windshield, did not have this trend of increased precipitation for the same period. Streamflow records from the Leadville area also do not indicate an increase in streamfiow from 1919 to 1938. The storm of July 27, 1937, considered one of the few, large, intense rainstorms at higher elevations, had a recorded precipitation of total 4.34 inches (4.26 inches in 1 hour). Streamflow-gaging-station records indicate that only 0.09 inch of storm runoff occurred. Paleoflood investigations of channels in the Leadville area and old newspaper accounts also indicate no substantial flood from this storm. This study indicates that the 1937 storm probably totaled about 1.7 inches of precipitation, much of which occurred as hail.     

黄土丘陵区降雨、径流、土壤水分的时空分布与利用对策

基于黄土丘陵区的延安燕沟多年监测资料，通过对燕沟流域的降雨、径流、及其不同土地利用方式下土壤水分等时空分布特征分析，明确了黄土丘陵区降雨的时间、空间分布具有显著差异性。降雨量在6～9月相对集中，年际、月际变异大；同时次降雨量、月降雨量均存在显著空间异质性，如降雨量沿燕沟沟道变化及坡向分异。径流特征是降雨及其下垫面特征的综合反映，3月左右由于气温上升，河道解冻，径流量出现小高峰，雨季后2个月出现最大高峰水量。对径流的利用则由于供水／需水时间错位，利用主要集中在枯水季节（4-6月），土壤水资源由于地形、降雨、植被覆盖等的差异性，特别是植被差异性利用，则存在时空异质性。土壤水分在雨季后1-2月在0～150cm形成高值期，150cm以下的土壤恢复缓慢。植被差异利用形成了土壤水分剖面不同：梯田〉草地〉拧条林〉拧条＋五角枫林〉沙棘林〉刺槐林。根据对水资源系统分析，提出了流域水资源开发利用的对策：农作物适雨种植制度；植被空间合理布局；降雨、土壤水、径流三水联合御旱，提高水资源利用效率。