基于MODCYCLE分布式水文模型的区域产流规律

为了分析区域产流时空变化规律以及不同下垫面的产流特征,采用了具有物理机制的分布式水文模型——MODCYCLE模型,并以天津市为例进行深入研究。该模型在综合考虑土壤、下垫面条件、降雨条件等多方面因素的基础上,采用修改后具有地表积水机制的Green-Ampt方程计算产流量。计算结果表明,1）1997－2004年天津市8 a平均总产流系数约为16%,其中陆面产流系数不足10%。2）陆面产流主要集中在北部山区、中心城区及东部沿海地区;水面产流主要集中在中部及东南部地区。3）陆面产流中城市区产流系数最大,8a平均为44.1%;农村居民地的产流系数也较大,为24.5%;天然林草和河滩地的产流系数不足10%,农田由于田埂的作用几乎不产流。     

Effects of shelter belts on fence-line pacing of deer and associated impacts on water and soil quality

Sustainable land use for deer farming requires the maintenance of good soil and water quality, which can be adversely affected by fence‐line pacing. This study tested the hypothesis that the absence or presence of shelter belts (one or two) in paddocks decreases fence‐line pacing and associated soil and water quality impacts. Soils near the fence line and in the rest of the paddock, in paddocks containing zero, one or two shelter belts, were sampled for bulk density and macroporosity (pores >30 μm diameter). Large intact samples (1 × 0.2 × 0.1 m³) were used to generate overland flow via rainfall simulation. The flow was tested for nutrients [phosphorus (P) and nitrogen (N) fractions], suspended sediment (SS), and the faecal indicator bacteria, Escherichia coli. Results showed that bulk density, void volume, SS, particulate P and total P were affected by location (fence line or rest of paddock) but, along with all other measurements except E. coli, were not affected by the number of shelter belts. Thus, the inclusion of shelter had no effect on the concentration of contaminant lost in overland flow or any soil physical or hydrological parameter, but decreased the run‐off of E. coli. The lack of contrast between the location of soils can be partly attributed to the soil type (Brown, NZ soil classification, USDA Taxonomy: Typic Fragiudalf), which when compared with past studies was less erosive and lost less P into solution. Other factors may have been different management or the lesser impact of weaners compared with older hinds and stags on soil properties. Although only E. coli concentrations were decreased by the inclusion of shelter, factors such as improved production and animal welfare weigh heavily in favour of installing and maintaining shelter on deer farms. However, the environmental benefit of shelter should be tested in other farms where factors such as slope, soil, climate and farm management may increase the contrast with no shelter.     

A relatively simple scaling method for describing the unsaturated hydraulic functions of stony soils

Few if any methods exist to estimate the effects of stone content (stoniness) on the unsaturated soil hydraulic properties. A relatively simple scaling method is presented to estimate the hydraulic conductivity of unsaturated stony soils having different stone contents. A key assumption of the method is that van Genuchten's water retention parameters α and n of the fine soil fraction are the same as those of the stony soil. The method further assumes a linearly decreasing relationship between the saturated hydraulic conductivity and the stone content, based on previous numerical simulations. Using the proposed method, it is possible to calculate the hydraulic conductivity of unsaturated stony soils, knowing the saturated hydraulic conductivity of the fine soil fraction, the retention curve of the fine soil fraction, and the particular stoniness of the soil.     

辽宁东部山区几种主要森林植被类型枯落物层持水性能研究

对辽宁东部山区6种主要森林植被类型枯落物的蓄积量及其持水性能进行的研究结果表明 :辽东山区森林枯落物蓄积量为5.4～39.0t·hm -2,针叶林的枯落物蓄积量明显高于阔叶林 (柞木林和杂木林 ) ,灌丛最少。枯落物总平均吸水速度1～4h变化最快 ,24h近乎为零 ,吸水达到饱和。针叶林枯落物半分解层持水率大于未分解层 ,前者最大持水率平均为234.8 % ,后者平均为176.5%;阔叶林则是未分解层持水率大于半分解层 ,前者最大持水率为600% ,后者为221.1 %。整个枯落物层最大持水率变化范围156.5%～494.6% ,平均值为267.5 % ,大小顺序是柞木林>杂木林>灌丛>红松林>落叶松林>油松林。整个枯落物层最大持水量变化范围为14.0～86.1t·hm -2 ,平均值为51.8t·hm -2 ,大小排序为红松林>落叶松林>柞木林>油松林>杂木林>灌丛 ;各林型的最大拦蓄率为67.0%～432.6 % ,平均值为196.7% ,大小排序为柞木林>灌丛>杂木林>红松林>落叶松林>油松林 ;各林型的最大拦蓄量为12.4～58.6t·hm -2,林型间平均值为34.1t·hm -2,大小排序为红松林>柞木林>落叶松林>油松林>灌丛 ;各林型的有效拦蓄率、有效拦蓄量同其相应的最大拦蓄率、最大拦蓄量表现特点相同 ,前者变化范围为43.6%～360.2%,林型间平均值为156.9%:后者的变化范围为10.3～45.7t     

HBV水文预报模型在白龙江流域的应用研究

[目的]在白龙江流域武都站以上区域构建HBV水文模型,通过对区域日径流模拟研究,来评估模型在该区域的适用性。[方法]在参数敏感性分析的基础上,对模型参数进行率定和验证,并分析径流和降水量的年际变化特征。[结果](1)在率定期Nash—Sutcliffe效率系数Ens=0.65,确定性系数R2=0.74,验证期Ens=0.60,R2=0.70,HBV模型在该流域模拟精度较高,具有较好的适用性;(2)降水量与模拟径流变化趋势对应,HBV模型较好地模拟出了洪水对降水的响应过程。[结论]HBV模型可进一步用于研究气候变化对白龙江流域水资源的影响。     

Monthly and seasonal streamflow forecasting of large dryland catchments in Brazil

Streamflow forecasting in drylands is challenging.Data are scarce,catchments are highly humanmodified and streamflow exhibits strong nonlinear responses to rainfall.The goal of this study was to evaluate the monthly and seasonal streamflow forecasting in two large catchments in the Jaguaribe River Basin in the Brazilian semi-arid area.We adopted four different lead times:one month ahead for monthly scale and two,three and four months ahead for seasonal scale.The gaps of the historic streamflow series were filled up by using rainfall-runoff modelling.Then,time series model techniques were applied,i.e.,the locally constant,the locally averaged,the k-nearest-neighbours algorithm(k-NN)and the autoregressive(AR)model.The criterion of reliability of the validation results is that the forecast is more skillful than streamflow climatology.Our approach outperformed the streamflow climatology for all monthly streamflows.On average,the former was 25%better than the latter.The seasonal streamflow forecasting(SSF)was also reliable(on average,20%better than the climatology),failing slightly only for the high flow season of one catchment(6%worse than the climatology).Considering an uncertainty envelope(probabilistic forecasting),which was considerably narrower than the data standard deviation,the streamflow forecasting performance increased by about 50%at both scales.The forecast errors were mainly driven by the streamflow intra-seasonality at monthly scale,while they were by the forecast lead time at seasonal scale.The best-fit and worst-fit time series model were the k-NN approach and the AR model,respectively.The rainfall-runoff modelling outputs played an important role in improving streamflow forecasting for one streamgauge that showed 35%of data gaps.The developed data-driven approach is mathematical and computationally very simple,demands few resources to accomplish its operational implementation and is applicable to other dryland watersheds.Our findings may be part of drought forecasting systems and potentially help allocating water months in advance.Moreover,the developed strategy can serve as a baseline for more complex streamflow forecast systems.     

Rainfall interception and stem flow by eucalypt street trees – The impacts of canopy density and bark type

Understanding how trees influence water movement in an urban landscape is important because in an ‘engineered xeriscape’ small changes in rainfall frequency or magnitude have significant implications to plant water availability and mortality at one extreme, and stormwater runoff and flooding at the other. This study relates direct measures of tree canopy interception and discusses their implication for catchment hydrology in different urban landscape contexts. We measured canopy throughfall and stemflow under two eucalypt tree species in an urban street setting over a continuous five month period. Eucalyptus nicholii has a dense canopy and rough bark, whereas Eucalyptus saligna has a less-dense canopy and smooth bark. E. nicholii, with the greater plant area index, intercepted more of the smaller rainfall events, such that 44% of annual rainfall was intercepted as compared to 29% for the less dense E. saligna canopy (2010). Stemflow was less in amount and frequency for the rough barked E. nicholii as compared to the smooth barked E. saligna. However, annual estimates of stemflow to the ground surface for even the smooth barked E. saligna would only offset approximately 10 mm of the 200 mm intercepted by its canopy (2010).Tree canopy and bark characteristics should be considered when planting in pervious green space, or impervious streetscapes, because of their profound impact upon tree and surrounding water availability, soil water recharge or runoff. This study provides an evidence base for tree canopy impacts upon urban catchment hydrology, and suggests that rainfall and runoff reductions of up to 20% are quite possible in impervious streetscapes. Street tree canopies can function as a cost-effective compliment to water sensitive urban design for stormwater reduction benefits.     

福建近海若干个拟投放深水网箱海湾理化环境调查与评估

根据2000和2001年福建主要港湾调查所获得的海洋水文和海洋化学环境资料，对拟投放深水抗风浪网箱海域的海水理化因子作了较详细的分析研究，以评估该海域是否适合于投放深水网箱。结果表明，三都澳、官井洋、东吾洋、罗源湾、福清湾、兴化湾，湄州湾和东山湾水深在25m以上，湾外有岛屿屏障，环境隐蔽、水流稳定，水温、盐度和透明度有显著的季节变化，pH和DO符合国家渔业水质标准，COD一般符合一类海水水质标准，局部海域达到二类海水水质标准，IN、PO3-P一般符合二类海水水质标准，在秋季有些港湾达到三类海水水质标准。从理化环境的角度分析，上述海湾可作为投放深水网箱之场所。     

基于遥感技术的珠三角6类林分的蒸散比研究

对珠江三角洲六类主要林分(区域)的蒸散发比进行了研究,6类林分包括桉树林、果树林、针阔混交林、灌木林、针叶混交林、阔叶混交林.同时对基于Priestley-Taylor扩展模型的物理机制进行分析与推理,发现可以通过MODIS和TM热红外数据计算的地温值来评估较大区域上的蒸散发能力,并结合2008-2009年的晴空数据进行计算分析.结果表明珠三角6类林分(区域)的蒸散发作用相当,桉树林并非耗水量最大的林种.     

Estimating Drainage under Cotton with Chloride Mass Balance and an EM38

Methodologies that use electromagnetic induction and resistivity in soil profiles to estimate drainage across whole fields and catchments require complex models or measurement systems that are not easily available or difficult to apply at the farm level. The objective of the present study was to define a methodology that could use information easily available to agronomists and commercial cotton consultants to estimate drainage in irrigated Vertisols using a chloride (Cl^?) mass balance approach. A secondary objective of this study was to eliminate or minimize the expensive and tedious laboratory analyses for determining Cl^? concentration in soils. A model was developed using electromagnetic induction measurements taken with an EM38 instrument in the horizontal mode (EM_H) to estimate the chloride concentration in a saturated soil extract in the 0- to 1.2-m depth of irrigated Vertisols. A stepwise linear regression model where the independent variables were soil water storage, exchangeable sodium percentage, and EM_H predicted chloride concentration the best. The chloride concentrations thus estimated were similar to measured values only when measured chloride concentrations in the saturated extract were ≤10 meq L^?1 (355 mg L^?1 = 240 mg kg^?1). These values of chloride were then inserted into a chloride mass balance model to estimate deep drainage. In more saline soils, large differences occurred between measured and estimated chloride. Values of drainage based on estimated chloride concentrations in the range of 0–10 meq L^?1 were very similar to those based on measured chloride concentrations. There is potential to use an EM38 for quick assessment of deep drainage under irrigated conditions in the field.