Length–weight relationships of five catfish species (Siluriformes) from the Ganga River,India

Knowledge of the length–weight relationships (LWRs) of fish is an important tool to understand fish body form, growth pattern, stock management and their conservation. The present study focused on investigating the length–weight relationships for five catfish species, Pachypterus atherinoides (Bloch, 1794), belonging to family Horabagridae; Batasio batasio (Hamilton, 1822) family Bagridae; Bagarius yarrelli (Sykes, 1839), family Gogangra viridescens (Hamilton, 1822); and Sisor rhabdophorus (Hamilton, 1822) belonging to family Sisoridae. Specimens were collected from the middle stretch of the Ganga River in India from November 2016 to May 2018. A total of 174 specimens of five fish species were collected, and their total lengths were measured to the nearest centimetre and the body weight to the nearest gram. The value of the parameter slope (b) of LWRs of the five species ranged from 2.86 (B. yarrelli) to 3.16 (G. viridescens), with a mean value of 2.99. The results of the present study documented the new maximum total length (TL) for P. atherinoides and S. rhabdophorus. The present study also provides the first reference regarding LWRs for S. rhabdophorus.     

Flooding tolerance of Sagittaria latifolia and Sagittaria rigida under controlled laboratory conditions

Pool‐scale growing‐season water‐level reductions (drawdowns) have been implemented on the Upper Mississippi River in an effort to improve fish and wildlife habitat. Aquatic vegetation is a key habitat component, with perennial emergent species, such as Sagittaria latifolia and Sagittaria rigida, especially important. River managers have assumed the need for continuous drawdown during the growing season with limited reflooding and used this guidance in assessing the potential for an ecologically successful drawdown. However, information on the effects of growing‐season flooding episodes on survival and growth of Sagittaria is limited. To assess the flooding tolerance of S. latifolia and S. rigida, we evaluated multiple levels of timing, duration, and depth on survival and productivity of plants. Plants were produced from S. latifolia and S. rigida seeds and S. latifolia tubers; all were reared under moist‐soil or shallow‐flooded rearing conditions. Mortality of plants was low (2%) among plants from large tubers, low (7%) among seedlings (and largely associated with early flooding treatments), and modest (11%) among plants from small tubers (with no clear effects of inundation). Flooding treatments generally had a positive effect on biomass production from seedlings, particularly when treatments occurred early, were relatively shallow, and were short in duration. There were no clear effects of depth, duration, or timing components of flooding treatments on plant biomass arising from tubers. This experiment indicates that S. latifolia and S. rigida are relatively tolerant of flooding events during the growing season and may actually benefit from some level of inundation.     

毛乌素沙漠南部植被指数的变化规律研究

为了认识毛乌素沙漠南部植被的变化,基于MODIS的NDVI遥感数据分析了2000-2013年毛乌素沙漠南部植被的变化特征,NDVI年平均值呈上升趋势,年增长率为2.69×10~(-3)/a。各年均值的空间最大值变化幅度不大,基本表现为上升趋势。结合转移矩阵的方法,将NDVI值分为不同级别并建立植被指数转移矩阵,计算分析了NDVI值逐年的级别转移情况。由各年NDVI值较上年的变化及各年植被覆盖级别较上年的变化分析显示,总体NDVI都表现为较上一年变好的趋势,2013年相对2000年的72.37%的像元的植被级别变好。将2013年相对2000年转移矩阵中NDVI值在各等级所占个数进行统计显示,NDVI值由矩阵的下三角向上三角转移,上三角阵中NDVI像元的个数远大于下三角阵,说明NDVI值表现出由低等级向高等级转化的趋势,植被情况逐步转好。整体上,2000-2013年毛乌素沙漠南部整体植被情况在持续转好。     

Impacts of the Victoria Nile Bujagali hydropower dam on fisheries and livelihoods

The Upper Victoria Nile (UVN) flows from Lake Victoria into Lake Kyoga, spanning 117 km and supports a diverse aquatic fauna that sustains livelihoods of riverside communities. The UVN is habitat to critically endangered (Labeo victorianus), near threatened (Oreochromis variabilis and Oreochromis esculentus), and rare species (Neochromis simotes). Four hydropower dams were built on the UVN to provide energy for industrial and socioeconomic development, notwithstanding consequential environmental and socioeconomic impacts. The impacts of Bujagali hydropower (BHP) dam on fisheries and livelihoods were assessed biannually (April and September) from 2006 to 2019, using fishing effort, species abundance, catch composition, and economic beach revenue at upstream, mid-reservoir, and downstream transects. The fishing boats increased from 31 in 2009 to 293 in 2019 and fishers from 83 to 500 over the monitoring period. Maximum annual catch of 461.4 t was recorded in 2014 and lowest of 54.2 t in 2009. In all transects, Protopterus aethiopicus and Labeo victorianus were least in the commercial catches and the use of Mormyrus kannume juveniles as bait for Nile perch fishery corresponded with increased catches from 3.3 t in 2009 to 148.2 t in 2019. Women were mostly engaged in post-harvest activities such as fish drying, smoking, and food vending. These observations suggest coupling effects of the hydropower dam and ineffective fisheries management. The harvest of M. kannume wild stocks for bait should be banned and research in possible domestication of the species undertaken. There is a need to strengthen fisheries enforcement to curb illegal effort and overexploitation and to implement conservation actions to mitigate potential biodiversity impacts from the hydropower dam operations.     

基于气候分区的甘肃省参考作物蒸发蒸腾量时空分布特征

参考作物蒸发蒸腾量(ET0)是计算作物需水量的重要参数,为了减少甘肃地区因地形和气候跨度大而引起的灌溉参数计算误差,根据甘肃省的地理特征和干湿程度将甘肃地区划分为陇南-甘南湿润区、陇中南部半湿润区、陇中北部半干旱区和河西干旱区4个区域,利用26个国家气象站点1980-2015年的逐日气象资料,采用FAO-56 Penman-Monteith方程计算ET0,并通过反距离权重空间插值法和偏相关分析法研究了甘肃省整体和不同分区ET0的时空分布特征和影响因素。结果表明:甘肃省ET0年际变化趋势为1980-1991年下降,1991-2015年上升,整体呈上升趋势;甘肃省ET0的空间分布总体为自东南向西北逐渐增加;ET0与日平均风速、日照时数、日最高气温、日最低气温、日平均气温均表现为极显著正相关,与平均相对湿度表现为极显著负相关,且影响程度顺序为,甘肃省:U>N>Tmax>RH>Tmin>Tmean,陇南-甘南湿润区:N>U>Tmax>RH>Tmin>Tmean,陇中南部半湿润区:N>U>RH>Tmax>Tmin>Tmean,陇中北部半干旱区和河西干旱区:U>N>Tmax>RH>Tmin>Tmean。结论:地形和气候对ET0影响很大,由湿润区向干旱区依次增加;各分区ET0差异较大,从东南部向西北部增加;甘肃省ET0主要影响因素为平均风速和日照时数。     

Distribution and carbon isotope composition of lipid biomarkers in Lake Erhai and Lake Gahai sediments on the Tibetan Plateau

Lipid biomarkers and carbon isotopes of n-alkanes, n-fatty acids, and n-alkan-2-ones were used to determine organic carbon sources to surface sediments in lakes Erhai and Gahai on the Tibetan Plateau. All sediment samples contained n-fatty acids with lower concentrations of n-alkanes and n-alkan-2-ones. Long chain n-alkanes in lake sediments were characteristic of a source mixture of epicuticular waxes of higher plants and submerged littoral zone plants while n-fatty acids sources were bacteria and floating and/or submergent macrophytes; the n-alkan-2-ones had a possible source in epicuticular waxes of higher plants and/or grass from catchment which entered the lake and were reworked by the microorganisms. Sediment samples examined from Lake Erhai had heavier δ¹³C values of bulk organic carbon and specific carbon compounds than samples from Lake Gahai and meadow soil. This heavier isotopic composition can be best interpreted by the enhanced productivity occurring in Lake Erhai due to its lower salinity and possibly to limited CO₂ concentrations; for the latter, this may have enriched ¹³C in the dissolved inorganic carbon pool of the lake water.     

Optimal allocation of water resources in large river basins: I. Theory

The major purpose of this paper is to present the useful techniques in the optimal allocation of water resources (OAWR) and to demonstrate using water resources applications how these methods can be conveniently employed in practice for systematically studying both simple and complex water resources problems. Formal modelling techniques in multiobjective decision-making provide many benefits to professionals working in water resources and elsewhere. A new Large-system Hierarchical Dynamic Programming (LHDP) method to solve the model can be carried out to ascertain the consequences of meaningful parameter changes upon the optimal or compromise solution.As a case study, the techniques and methods are applied to the OAWR of the Yellow River Basin (YRB) of China. The next paper shares with the reader recent research results on the OAWRYRB.Notation L _i inflows from the trunk stream in the subregioni. - S _i run-off volume of the river sectioni. - Q _i net inflows of intervals in the subregioni. - W _i volumes of water drawn the trunk stream ofi into subdistricti. - H _i volumes of water returning to the trunk stream in the subdistricti. - B _i(W _i) the maximum net benefits (in hundred million yuan) from the annual-water consumption ofW _iin subregioni. - W _ik the annual-water consumption (in hundred million m³) of sectorK in subregioni, k = 1, 2, 3, 4. - B _ik(W _ik the maximum net benefits (in hundred million yuan) from the annual consumptionW _ikof sectork in subregioni. - BS _i(S _i) the maximum net benefits (in hundred million yuan) obtained from the optimal allocation of the run-off volumeS _iof river trunki among different sectors within the months of a year.     

Spawning and recruitment patterns of major fish species in Bontanga Reservoir, Ghana, West Africa

The spawning and recruitment patterns of the major Cichlid fish species, including Hemichromis fasciatus, Oreochromis niloticus, Sarotherodon galilaeus, Tilapia zillii and other species, Auchenoglanis occidentalis, Brycinus nurse, Clarias gariepinus and Marcusenius senegalensis were studied for 24 months in Bontanga Reservoir, Ghana, using length‐based fish stock assessment approaches. The species spawned throughout the year, with two spawning pulses described as major and minor spawning seasons. The major spawning season occurred from March to September for the Cichlids, and from May to September for the other species. The minor spawning season, indicative of extended spawning, occurred from October to March for all the fish stocks. Fish spawning began with the onset of the rains in April/May, peaking by June/July, before the rainfall peak in August for all the fish stocks studied. Recruitment was found to occur throughout the year, with major and minor pulses coinciding with the major and minor spawning seasons. Accordingly, the most appropriate time for a possible closed fishing period appears to be from June to August, 1 month after the start of, and before the end of, the rains. The estimated mean standard length (L_m) for first time spawners of A. occidentalis, B. nurse, C. gariepinus and H. faciatus were 11.7, 12.7, 2.7 and 7.5 cm respectively. The estimated maturity–length ratio of 0.4 and 0.2 for O. niloticus, S. galilaeus and T. zillii were lower than the known 0.7 for normal growth, suggesting the tilapias matured faster, and at a smaller size, in the reservoir. Apparent sexual precocity associated with early maturity, year‐round spawning and recruitment were some important adaptations found to have sustained the reservoir fisheries, even during high fishing pressures. For conservation and sustainable exploitation of the fisheries, instituting a closed fishing season, mesh size regulations, withdrawal rights and a community‐based fishery management system are recommended.     

Is sluice gate management beneficial for spawning migrations? The case of the shark catfish (Helicophagus waandersii) in the Mun River below the Pak Mun Dam,Thailand

The reproductive ecology of shark catfish Helicophagus waandersii in the Mun River, the largest Mekong tributary in Thailand, was studied from July 2003 to December 2004. The aim of the study was to determine whether shark catfish, which contribute greatly to fish catches, benefits in terms of spawning, from the management regime of the Pak Mun Dam to open all sluice gates annually for 4 months during the rainy season. In total, 228 females were studied. The highest average gonadosomatic index (4.42% ± 1.90%) was observed in the rainy season in June 2004. Fecundity ranged from 21 550 to 191 540 eggs. Three hormonal profiles viz. testosterone (T), 17 β‐estradiol (E₂), and 17, 20 β‐dihydroxy‐4‐pregnen‐3‐one (17, 20 βP) were determined by radioimmunoassay. The highest levels of T (0.96 ng ml⁻¹), E₂ (14.37 pg ml⁻¹), and 17, 20 βP (0.81 ng ml⁻¹) were respectively measured in April to May, July, and May. Changes in the maturity stage and the annual sex hormonal profiles revealed that the spawning period of H. waandersii is from May to June. There was no spatial statistical difference (p > 0.05) for each sex steroid profiles. The results indicated that H. waandersii spawn during the rainy season in the rapid areas, both downstream and upstream, and the sluice gates opening management regime for 4 months in the rainy season is of advantage for H. waandersii in terms of feeding and nursery grounds in the upstream area. Copyright © 2006 John Wiley & Sons, Ltd.     

Development of Habitat Suitability Criteria and In‐Stream Habitat Assessment for the Benthic Cyanobacteria Phormidium

Global demand for freshwater has led to unprecedented levels of water abstraction from riverine systems. This has resulted in large alterations in natural river flows. The deleterious impacts of reduced flows on fish and macroinvertebrate abundances have been thoroughly investigated; in contrast, there is a limited understanding of the potential for changes in the abundance of nuisance benthic algal/cyanobacterial blooms. In New Zealand, Phormidium sp. blooms are common in numerous rivers during summer low flows. In this study, an in‐stream habitat assessment is used to examine the relationship between Phormidium habitat availability and reducing flows. Over 650 observations of Phormidium mats, from seven sites (Hutt River, lower North Island, New Zealand), were used to construct habitat suitability curves for depth, velocity and substrate. Preference curves were fitted using both the ‘forage ratio’ and ‘quantile regression’ methods. Phormidium growth, observed at all seven sites, increased significantly from upstream (uppermost site, 5.2% mat cover) to downstream (63.5%). The habitat suitability curves revealed Phormidium had a large tolerance to velocity, depth and substrate type. Consequently, decreases in flow had only negligible effects on available Phormidium habitat. During periods of stable flow, Phormidium abundance positively correlated with increased nitrogen concentrations, potentially explaining the large variation in Phormidium cover from upstream to downstream. Quantile regression generated habitat suitability criteria were a more accurate predictor of available Phormidium habitat than the forage ratio criteria. Copyright © 2013 John Wiley & Sons, Ltd.     

Long‐term changes in flow regime and fish assemblage composition in the guadalupe and san marcos rivers of texas

Riverine flow regimes are naturally dynamic, but become increasingly homogenized following anthropogenic flow alteration. Loss of dynamism disrupts naturally occurring structuring mechanisms within the associated biotic communities, at times causing shifts in composition. Here we considered how stream fish assemblages in two Central Texas rivers changed after alteration of flow regime by either construction of a mainstem, deep storage reservoir or flood‐retaining structures. Following impoundment, number of large and small floods increased from 0.81 to 1.07 floods per year (FPY) in the upper Guadalupe River, decreased from 0.84 to 0.42 FPY in the lower Guadalupe River and decreased from 0.87 to 0.7 FPY in the San Marcos River. Historical ichthyofauna data ranging from 1938 to 2006 were used to assess changes in assemblage composition and species abundance. Assemblages did not differ in the upper Guadalupe River (Bray–Curtis index = 37.4%; ANOSIM global R = 0.079, p = 0.08), but did differ in the lower Guadalupe River (25%; global R = 0.409, p < 0.01) and San Marcos River (27%; global R = 0.19, p < 0.01). In general, habitat generalist species dominated assemblages during periods of reduced flood frequencies (i.e. drought of record; following impoundment), whereas regionally endemic species (N = 3) and substrate and broadcast spawning species (N = 5) declined (b₁ < 0; α = 0.05). Based on the results from this study, managing flows in the lower Guadalupe River to mimic historical timing of flood pulses might attenuate contemporary disruption of natural assemblage composition. Copyright © 2010 John Wiley & Sons, Ltd.     

Analytical solutions of unsteady drainage problems for soils subjected to variable recharge from a semi-confined aquifer

In drainage of agricultural lands, the upward vertical recharge from a semi-confined aquifer depends on the difference of the piezometric heads on the two sides of the semi-impermeable layer through which this recharge takes place. This means that the recharge through the semi-impermeable base depends on the unknown height of the unsteady water table. In the nonhomogeneous Boussinesq equation, which describes the drainage problems, the downward uniform rate of the recharge from rain or irrigation and the recharge from the semiconfined aquifer are expressed by two terms. By solving the Boussinesq equation expressions for the nondimensional height of the water table and the nondimensional discharge of the drains per unit drained area are obtained for three different initial conditions. Some known solutions are shown as special cases of the present solutions. Variation of nondimensional water table heights at half distance of the drain spacing and the nondimensional discharge of the drains with nondimensional time have been graphically illustrated with the help of synthetic examples.Notation B _s thickness of the semi-impervious layer [L] - c hydraulic resistance of the semi-impervious layer [T] - D depth of the drains from the base [L] - d _e equivalent depth [L] - h=h(x, t) height of the water table [L] - h ₀ initial height of the water table [L] - h _t water table height at mid-distance of drains att [L] - h _j ,h _k water table height at mid-distance of drains at timej andfk, respectively [L] - H ₀ piezometric head in the semi-confined aquifer [L] - K hydraulic conductivity of the soil [LT^–1] - K _s hydraulic conductivity of the semi-impervious layer [LT^–1] - k ₀,k ₁,k ₂ nondimensional constants - L distance between the drains [L] - q ₀ upward recharge per unit surface area through the semi-impervious layer [LT^–1] - q _t discharge per unit drainable area of drains at timet [LT^–1] - R,R ₀ recharge per unit surface area from rain or irrigation during the unsteady and steady-state, respectively, [LT^–1] - S specific yield of the soil - t time of observation [T] - x distance measured from the drain [L] - leakage factor [L] - nondimensional distance - nondimensional time     

Effects of atmospheric exposure on chlorophyll a,biomass and productivity of the epilithon of a tailwater river

Field experiments were conducted to determine the effects of atmospheric exposure on the chlorophyll a content, biomass and gross primary productivity (GPP) of littoral epilithon in the Colorado River below Glen Canyon Dam, Arizona. The chlorophyll a content of the epilithon was much more sensitive to exposure than the biomass. The epilithon was rapidly bleached during summer daytime exposures, but algal filaments remained attached for several weeks after reinundation. The percentage of initial chlorophyll a remaining after one day of exposure was not different from the percentage remaining after two days of exposure. However, significant reductions in chlorophyll a content were detected for daytime exposures as short as six hours. Overall, there were close inverse relationships (r² ≥ 0–73) between the time exposed or cumulative solar radiation (400–700 nm) and the percentage of initial chlorophyll a remaining after reinundation. The GPP of Cladophora glomerata-dommaled epilithon from the permanently inundated channel was 10 times higher than the GPP of epilithon from the zone of daily water level fluctuation. Experimental atmospheric exposure of the epilithon from each zone reduced the GPP, but not the assimilation ratio (GPP per unit of chlorophyll a) of the epilithon. The Glen Canyon epilithon has low resistance to exposure disturbances, and recolonization is slow under hydropower peaking flow regimes. Cladophora glomerata has an important structural role in Glen Canyon, the disruption of which is likely to precipitate effects at higher trophic levels.     

某水电站琴键堰体型优化试验研究

琴键堰是一种新型的高效溢流堰,以曲折的堰顶结构来增加溢流前缘总长度,使得其泄流能力远超直线堰。针对某拟建水电站琴键堰泄流能力不足的问题,提出了增加展宽比(L/W)、增加堰高(P)和增加堰高且减少单元数(n)的优化方案,并通过物理模型试验进行验证,得到了满足设计要求的推荐方案。此外,本研究还探讨了水工模型类别(整体及断面模型)和比尺效应对琴键堰泄流能力的影响。通过对比分析优化方案可知：方案M1(展宽比L/W由7.75增至8.88)中,琴键堰泄流能力得到了一定程度的提高,但泄流能力仍不满足设计要求;方案M2(堰高由4.50 m增至6.50 m)和M3(堰高由4.50 m增至6.90 m,单元数由17.5个减至8.5个)中,琴键堰泄流能力显著增加,该两种方案皆可满足设计要求。试验结果表明：与琴键堰整体模型相比,其断面模型测得的泄流能力偏大约6%;对于琴键堰,当模型堰上水头大于2.50 cm时,比尺效应对琴键堰泄流能力的影响可以忽略。     

Tree colonization trends on a sediment bar after a major flood

Tree mortality and regeneration in riparian areas are greatly influenced by flooding. The elevational distribution of Salix spp. and Robinia pseudoacacia were investigated by observing densities and standing conditions before and after a major flood on a sediment bar in the middle reaches of the Arakawa River in Kumagaya, Japan. The subsequent tree recruitment was also examined. R. pseudoacacia was easily washed away with the eroded sediment, whereas Salix spp. was found to be more tolerant. Both species were able to survive even after collapsing, provided that their roots were fully or partially embedded in the sediment. Re‐shooting of collapsed trees, rather than emergence from saplings (either by seeds or vegetative fragments), was observed to be the major method of recruitment after the flood. Therefore, tree density before the flood was unchanged, unless the trees were subject to washing away. Salix spp. recruitment was mainly observed in low‐lying areas and R. pseudoacacia in elevated areas. Recruitment from saplings was species‐specific. Salix spp. at high elevations originated mainly from shoot fragments as they need high levels of moisture for seed germination and at higher elevations, sediment moisture content is very low. R. pseudoacacia, on other hand, originated mainly from roots and seeds. At a given elevation, past recruitment patterns indicated that the annual recruitment of trees increased with tree density up to a particular threshold of recruitment density. Further increases in tree density beyond that optimum value resulted in a decline in recruitment. Furthermore, threshold density was observed to increase along with elevation for R. pseudoacacia while declining with Salix spp. Copyright © 2010 John Wiley & Sons, Ltd.     

阿克苏河流域不同植被类型NDVI时空变化特征

归一化植被指数(NDVI)是反映地表植被生长状况的一类敏感的光谱信号。利用NDVI反演新疆阿克苏河流域内的植被覆盖及动态变化特征,有利于及时准确地获取流域内植被的时空分布,在气候变化背景下深入研究阿克苏河流域植被的生长及变化特征,具有重要意义。根据土地利用类型划分标准,结合研究区现状,将阿克苏河流域植被分为林地、灌木林地、草地、园地和耕地共5种类型,利用2000年2月-2014年12月NDVI 16 d逐月合成数据,分析了研究区不同植被类型的NDVI在各生长阶段的数量变化特征,拟合了不同植被类型的生长状况及其变化曲线。研究结果表明:2000-2014年,阿克苏河流域林地、灌木林地和耕地的NDVI整体呈下降趋势,草地和园地的NDVI则呈现上升趋势;各类植被的NDVI最低值均出现在冬季(1-2月),峰值则出现在夏季(7-8月);NDVI值急剧上升阶段处于3-5月,下降阶段处于9-11月;耕地和园地覆盖度明显增加,林地、灌木林地和草地覆盖度则呈现减少趋势。     

滇池高等沉水植物50年变迁状况对生态修复的启示

跟踪滇池50年来高等沉水植物的演变状况,不但可以更为客观和综合地评判滇池水生态状况及其变化动向,还可以为沉水植物的修复提供科学依据。研究表明,1957—2010年间,滇池共出现高等沉水植物22种,其中1957—1963年19种,1975—1977年11种,1981—1983年13种,1995—1997年和2001年均10种,2008年8种,2010年7种,总体呈现出明显的减少趋势。根据各时段出现的频率,确定穗状狐尾藻(Myriophyllum spicatum)、马来眼子菜(Potamogeton malaianus)和篦齿眼子菜(Potamogeton pectinatus)3种沉水植物可作为滇池生态修复先锋物种;黑藻(Hydrilla verticillata)、菹草(Potamogeton crispus)、苦草(Vanllisneria natans)和金鱼藻(Ceratophyllum demersum)4种植物可作为较早恢复和种植的对象。微齿眼子菜(Potamogeton maackianus)、穿叶眼子菜(Potamogeton perfoliatus)和大茨藻(Najas marina)可在滇池沉水植物生态恢复中期工程中使用。     

On the parametric approach to unit hydrograph identification

Unit hydrograph identification by the parametric approach is based on the assumption of a proper analytical form for its shape, using a limited number of parameters. This paper presents various suitable analytical forms for the instantaneous unit hydrograph, originated from known probability density functions or transformations of them. Analytical expressions for the moments of area of these form versus their definition parameters are theoretically derived. The relation between moments and specific shape characteristics are also examined. Two different methods of parameter estimation are studied, the first being the well-known method of moments, while the second is based on the minimization of the integral error between derived and recorded flood hydrographs. The above tasks are illustrated with application examples originated from case studies of catchments in Greece.Notations A catchment area - a,b,c definition parameters (generallya is a scale parameter, whileb andc are shape parameters) - C _v coefficient of variation - C _s skewness coefficient - D net rainfall duration - f( ) probability density function (PDF) - F( ) cumulative (probability) distribution function (CDF) - g( ) objective function - H net rainfall depth - H ₀ unit (net) rainfall depth (=10 mm) - I(t) net hyetograph - i(t) standardized net hyetograph (SNH) - I _n n ^th central moment of the standardized net hyetograph - Q(t) surface runoff hydrograph - q(t) standardized surface runoff hyrograph (SSRH) - Q _n n ^th central moment of the standardized surface runoff hydrograph - S _D (t) S-curve derived from a unit hydrograph of durationD - s(t) standardizedS-curve (SSC) - t time - T _D flood duration of the unit hydrographU _D (t) - T ₀ flood duration of the instantaneous unit hydrographU ₀(t) (= right bound of the functionU ₀(t)) - t _U IUH lag time (defined as the time from the origin to the center of area of IUH or SIUH) - t _I time from the origin to the center of the area of the net hyetograph - t _Q time from the origin to the center of the area of the surface runoff hydrograph - t _p time from the origin to the peak of IUH (or SIUH) - U _D (t) unit hydrograph for rainfall of durationD (DUH) - U _o (t) instantaneous unit hydrograph (IUH) - u(t) standardized instantaneous unit hydrograph (SIUH) - U _n nth central moment of area of IUH - U _n nth moment of IUH about the origin - U _n nth moment of IUH about the right bound (when exists) - V surface runoff volume - V ₀ volume corresponding to the unit hydrograph     

TRMM卫星降水产品在尼洋河流域的适用性定量分析

作为地面雨量站资料的重要补充,卫星降水产品对资料短缺或无资料地区尤为重要。位于我国高寒山区的尼洋河流域属于典型的资料短缺地区,根据5个气象站点2001-2016年的月降水数据和中国地面降水日值格点数据集2001-2013年的日降水资料,利用反距离权重插值法对其进行处理,在尼洋河流域分别对月、日尺度数据用相关系数(R)和相对误差(BIAS)检验TRMM降水数据的精度。结果表明:在时间尺度上,TRMM月降水数据与实测数据在流域整体上一致性良好(R=0. 90),而日降水数据的一致性较差(R=0. 29),且BIAS较大;在单一站点上,TRMM月降水数据的精度较高(R 0. 9),而日尺度R 0. 50,精度较低。在空间尺度上,通过克里金插值法得到TRMM降水精度的空间分布,月降水精度由西向东逐渐减小,而日降水的精度与之相反。整体上,TRMM月降水数据精度高,具有较好的适用性,根据TRMM月降水数据分析尼洋河降水时空分布特征。结果显示尼洋河流域降水大都集中在5月至9月,而11月至次年2月,降水量很少;年降雨量呈现由西北向东部逐渐递增的趋势,不同区域降水量差异较大。     

富营养化水体中盐度对香蒲去除氮磷作用的影响

针对含盐量高的富营养化水体,采用桶栽方式研究了盐度对香蒲去除富营养化水体中氮磷的影响。结果表明,在盐度范围为0~1.00%时,香蒲可快速、高效地去除水体中的氮磷等营养物质。但水体中NH_4~+-N、TN和TP的去除率整体随盐度增加而呈下降趋势,盐度的增加引起了植物某些生理特性的改变,NaCl胁迫下香蒲叶片组织中叶绿素含量均较对照显著下降。较高盐度(1.00%)胁迫下,香蒲会通过积累脯氨酸来调节体内细胞的渗透势,但叶片组织中丙二醛含量会显著增加,植物叶片组织的细胞膜系统受到伤害。香蒲在盐胁迫下生理生化指标的变化与其对富营养化水体中氮磷的去除效果具有一致性。