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71.
The Dead Sea, the Holocene terminal lake of the Jordan River catchment, has fluctuated during its history in response to climatic change. Biblical records, calibrated by radiocarbon-dated geological and archaeological evidence, reinforce and add detail to the chronology of the lake-level fluctuations. There are three historically documented phases of the Dead Sea in the Biblical record: low lake levels ca. 2000–1500 B.C.E. (before common era); high lake levels ca. 1500–1200 B.C.E.; and low lake levels between ca. 1000 and 700 B.C.E. The Biblical evidence indicates that during the dry periods the southern basin of the Dead Sea was completely dry, a fact that was not clear from the geological and archaeological data alone. 相似文献
72.
An experiment on evapotranspiration from citrus trees under irrigation with saline waterwas carried out for 4 months. Two lysimeters planted with a citrus tree in the green house wereused. One lysimeter was irrigated with saline water (NaCl and CaCl2 of 2000 mg/L equivalence,EC = 3.8 dS/m, SAR = 5.9) and the other was irrigated with freshwater using drip irrigation. Theapplied irrigation water was 1.2 times that of the evapotranspiration on the previous day.Evapotranspiration was calculated as the change in lysimeter weight recorded every 30 minutes.The lysimeters were filled with soil with 95.8% sand. The results of the experiment were as follows.(i) The evapotranspiration from citrus tree was reduced after irrigation with saline water. Theevapotranspiration returns to normal after leaching. However it takes months to exhaust the saltfrom the tree. ( ii ) To estimate the impact of irrigation with saline water on the evapotranspirationfrom citrus trees, the reduction coefficient due to salt stress (Ks) was used in this experiment.Evapotranspiration under irrigation with saline water (ETs) can be calculated from evapotranspira-tion under irrigation with freshwater (ET) by the equation ETs = Ks× ET. Ks can be expressed as afunction of ECsw. (iii) The critical soil-water electrical conductivity (ECsw) is 9.5 dS/m, beyondwhich adverse effects on evapotranspiration begin to appear. If ECsw can be controlled at below9.5 dS/m, saline water can be safely used for irrigation. 相似文献
73.
Water resources for agricultural development and landscape enhancement in Kuwait are very scarce; the quality is saline (brackish), and the soil texture is sandy, incapable of holding nutrients and moisture. Most of the rainfall in Kuwait either evaporates due to the high temperatures or percolates through the soil. The rainfall is not sufficient to recharge the underground water supply. A variety of alternative water sources have been studied, including seawater desalination and wastewater treatment. Wastewater treatment proved to be convenient due to the relatively low salinity detected in the treated water. Furthermore, the amount of wastewater is expected to increase as more residential areas are connected to the sewage system as the population increases.
The development of a greenery plan for Kuwait requires intensive water management. This goal can be achieved through manpower training in landscape development, selection of plants tolerant to arid environments, usage of appropriate irrigation and drainage systems, promotion of greenery programs within public and the governmental agencies for their direct participation in urban area beautification, and extension of wastewater treatment techniques. 相似文献
74.
两个相连湖泊的微生态系统——云南高原湖泊中浅水的星云湖和深水的抚仙湖研究 总被引:4,自引:0,他引:4
抚仙湖是中国云南省的一个深水湖,连接着富营养化的浅水湖--星云湖,星云湖排放含绿藻的水进入抚仙湖。两湖位于省会昆明附近,由于地方文化、集约化农业、以及旅游业的发展,两湖已经富营养化。因为湖泊体积容量的级别差异,深水湖的富营养化几乎没被注意,抚仙湖秋季下层滞水带缺氧已经关注了20年,似乎下层滞水带是深水湖富营养化的指标或趋势。抚仙湖看起来目前情况尚好,可以说寡营养,然而,外界负荷是潜在的,且是以稳定的加速度进行的。在此对浅水湖富营养化的原因进行了讨论,包括在其它云南湖泊观察到富营养化的过程,再者,对两个连相湖的藻和蓝藻碎片的大小构成进行比照。为了与深水的抚仙湖状况进行比较,简略介绍了一个日本的深湖及其径流系统。其中,涡流和它的微生态系统,在两者中相关性很好。对于以涡流生态系统的见解判断微生态系统的深水湖富营养化问题将给予概括。 相似文献
75.
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77.
介绍了当前湖泊水下地形测量的一般方法和作业过程。针对逐点插入构建不规则三角网算法,本文提出了效率改正算法和格网索引号快速计算算法。基于不规则三角网,给出了湖泊水下数字高程模型的一般应用模型——任意点高程计算、填挖方计算模型及等深线计算模型。 相似文献
78.
Multi-parameter studies (stable isotopes in carbonate and organic matter, pigment,organic carbon and nitrogen contents) from a 660-yr continuous sediment core from Lake Cheng-hai, a closed, eutropic lake in southern China, provide information on lake historical eutrophi-cation. During the last 660 years, great changes have taken place in productivity and eutrophi-cation of Lake Chenghai in response to human activities. In 1690, the productivity of the lakebegan to increase as Lake Chenghai became closed from agriculture in the lake‘‘ s watershed. In 1942, Lake Chenghai evolved to eutrophic state, marked by an increase in organic carbon, ni-trogen, CaC03, pigment contents and obvious negative values of stable isotopes, which is more or less simultaneous with the large-scale population immigration during the period. In 1984, in-tensive human activities induced modern lacustrine productivity and eutrophic level. Human-in-duced trophic changes during the past few decades have affected the Lake Chenghai ecosystem tosuch an extent that it has never experienced before in the last 660 years. 相似文献
79.
莱州湾南岸平原是指西起小清河口,东至胶莱河口的广大沿岸地区,这一地区近年来是我国工农业发展较快的地区,也是我国地下咸水入侵较为严重的地区。历史上,莱州湾南岸平原地区曾有一些湖泊存在,如巨淀湖、黑冢泊、别画湖,但现在早已荡然无存了。研究这些古湖泊的消亡原因对于恢复该区古地理环境以及确立湖迹区今后的发展方向具有十分重要的意义。本文运用查阅历史文献、地层剖面分析、地名考证、遥感解译等多种方法,对莱州湾南岸古湖泊的消亡原因进行了研究与分析,并指出该区古湖泊消亡的原因是气候变干、河流变迁、人类活动影响等,其中气候变化是古湖泊消亡的根本原因,河流变迁是古湖泊消亡的直接原因,而人类活动则加速了古湖泊消亡的进程。 相似文献
80.