香蒲对水体的净化效应

为了研究香蒲对水体的净化效应,为衡水湖的治理提供科学的理论根据。于2005年不同时间对大量生长香蒲区和无香蒲区的水样进行NH4+-N、NO2--N、总磷和水硬度的测定,通过时空水质分析研究了香蒲对水体的净化效应。香蒲对NH4+-N有明显的吸收作用,且不同生长阶段对NH4+-N的影响不同,营养生长旺盛阶段对NH4+-N的影响最大,但在高温季节大量香蒲残体分解已使湖水严重污染;香蒲对NO2--N无吸收作用,对衡水湖的影响是间接的;香蒲对总磷有明显的吸收作用,对水硬度没有明显的影响。香蒲的生长对氮、磷有吸收作用,其营养生长旺盛时期效果更加明显。香蒲有利于富营养化水体的净化。     

三峡枢纽修建后对洞庭湖治理方略的研究

本文简述了历史上长江与洞庭湖的复杂关系及治理过程，提出三峡枢纽修建后根治洞庭湖的设想和水利、交通等的具体布署方案，并描述了洞庭湖根治后的前景。     

微灌用沉沙池泥沙沉降计算方法试验研究

对沉沙池设计中最常用的准静水沉降法和一维流超饱和输沙法进行了比较研究,得到了该两种方法用于微灌沉沙池设计中的参数变化范围,并对其中的紊动修正系数K和恢复饱和系数a进行了专门试验研究,得出了K和a的计算公式和适用条件.试验结果表明:准静水沉降法的计算误差较大,但在一定范围内,可以满足精度要求,用来估算沉沙池池长;一维流超饱和输沙法计算简单并且具有较好的计算精度,可以用于微灌用沉沙池的工程设计计算.     

Temporal and spatial variations of evapotranspiration for spring wheat in the Shiyang river basin in northwest China

The methods for estimating temporal and spatial variation of crop evapotranspiration are useful tools for irrigation scheduling and regional water allocation. The purpose of this study was to develop a method for mapping spatial distribution of crop evapotranspiration and analyze the temporal and spatial variation of spring wheat evapotranspiration in the Shiyang river basin in Northwest China in the last 50 years. DEM-based methods were employed to estimate the spatial distribution of spring wheat evapotranspiration (ET_c). Reference crop evapotranspiration (ET₀) was calculated with the Penman–Monteith equation using meteorological data measured from eight stations in the basin. Crop coefficient (K_c) was determined from measured evapotranspiration in spring wheat season in the region. The results showed that ET_c gradually increased in the upper reaches of the basin in the last 50 years, while the middle reaches showed a significant decreasing trend, and in other regions, no significant trend was found. These changes can be attributed to expansion of irrigation areas and climate change. The multiple regression analysis between ET_c and altitude, latitude, and aspect were carried out for eight weather stations and the relationships were used to map ET_c for the basin. The spatial variations of ET_c were analyzed for three typical growing seasons based their precipitation. Results showed that long-term average ET_c over cultivated land was increasing from 270 mm in southwest mountainous area to 591 mm in northeast oasis of the basin, and the relative error between the estimated ET_c in spring wheat growing season by reference evapotranspiration (ET₀) and crop coefficient (K_c), and the interpolated ET_c was within 11.1%.     

滇中洱海流域水资源配置初步研究

根据云南滇中水资源系统特点，采用四层网络的滇中水资源大系统优化配置结构，建立了以缺水量最小为目标的水资源配置模型。结合水资源系统分区及各区运行调度规则，以洱海流域片区为例，采用常规模拟技术对模型进行求解，得出了洱海片区各计算单元四个水平年水资源供需平衡结果及各区的调水方案等水资源配置初步成果，分析了解决缺水的可能途径。     

1QD型垄向区田筑挡机工作机组的受力分析

分析了垄向区田筑挡机在工作时的受力情况以及铲板入土的最佳角度,为该机具的参数设计提供了理论依据,证明了筑挡机的可行性,推动了垄向区田技术的发展。     

On the limnology of Salda Lake,a large and deep soda lake in southwestern Turkey: future management proposals

• 1. The limnological characteristics of Salda Lake, a deep, soda and highly alkaline lake in the Lake District of southwestern Turkey, are presented.
• 2. Physical and chemical variables indicate that the lake is composed of hydrochemically different water layers formed by groundwater sources located on the floor of the lake.
• 3. Phytoplankton and zooplankton are characterized by a limited number of species and low dominance reflecting the extreme conditions of the lake.
• 4. Hydromagnesite stromatolites occur all around the lake margins.
• 5. The lake is threatened by falling water levels and organic pollution. Recommendations for the conservation of the lake are presented.

Copyright © 2004 John Wiley & Sons, Ltd.     

Survival and Growth of Bighead Carp Fry Exposed to Low Salinities

Bighead carp (Aristichthys nobilis Oshima) fry of various ages (11, 18, and 35 days post-hatch) were exposed to the low salinities encountered during the annual intrusion of seawater in Laguna Lake, Philippines. Practical indices of salinity tolerance assessed the effect of a 96 h direct exposure to low salinities (0–16). Mean (MST) and median survival times (MST50) of fry decreased as salinity of rearing medium increased. Younger fry were less able to tolerate exposure to these salinities than their older cohorts. Median lethal salinity after 96 h (MLS) revealed higher tolerance among 35–day old fry (7.6) than 11 (2.3) and 18–day old fry (6.0), demonstrating that survival in saline water depends on their age at initial exposure to low salinities. Mean body weight of 18–day old fry reared in 0 and 2 for 3 and 4 weeks was higher than for those reared in 4 and 6 for the same period. Growth over these periods was inversely related with the range of salinities tested. These results demonstrate that, despite their known stenohalinity, bighead carp fry possess some degree of osmoregulatory capability, allowing them to survive and grow in lakes subjected periodically to saltwater inflow.     

Genetic differentiation of the bronze featherback Notopterus notopterus between Mekong River and Tonle Sap Lake populations by mitochondrial DNA analysis

ABSTRACT:   Although the bronze featherback Notopterus notopterus is an important fish in South-East Asia, the population structure has not been investigated. In this study, genetic diversity and population structure of the bronze featherback were examined using nucleotide sequence analysis of the mitochondrial DNA control region for 332 fish collected from Tonle Sap Lake and the Mekong River in Cambodia. The average nucleotide diversity (π) of all samples was 0.033, and the Mekong River samples had higher nucleotide diversity (0.034) than Tonle Sap Lake samples (0.028). The nucleotide diversity between the lake and river samples varied from 0.029 to 0.037. The genetic differentiation between the river and lake populations was also supported by the pairwise F -statistic values and hierarchical analysis of molecular variance, indicating that the Tonle Sap Lake population is genetically isolated from the population in main stream of the Mekong River.     

Determination of spermatological properties of male Liza abu (Heckel, 1843) in Atatürk Dam Lake, Şanlıurfa

The aim of this study was to determine the spermatological characteristics in male L. abu during the spawning season. Semen was collected weekly by abdominal massage from 26 males in March. In collected semen, volume, motility, duration of motility, concentration and pH were determined. In the L. abu sperm, volume (μl), motility (%), duration of motility (s), concentration (×10⁹/ml), and pH values were found 45.76 ± 3.55, 54.25 ± 2.93, 330.15 ± 37.92, 4.27 ± 0.40 and 7.87 ± 0.05, respectively. A correlation was found between semen volume and semen pH. Semen volume and the duration of sperm motility were higher in the 2nd and 3rd sampling dates than in the 1st and 4th sampling dates (P < 0.05; P < 0.01, respectively). Neither sperm motility nor sperm concentration was affected by sampling dates. Major changes in semen pH were observed in the 4th sampling date (P < 0.001). The Pearson correlation test presented significant relationships with the duration of motility, semen volume, and motility. Semen pH values were significantly correlated with the sperm concentration and semen volume. Sperm concentration was inversely correlated with semen volume. Sperm motility and duration significantly correlated with total weight. Total length significantly correlated with the duration of motility and total weight. In conclusion, these characteristics represent a valuable baseline dataset for establishing a semen quality standard and provide background information that may be useful for assisted breeding programs in this species.