Tank-reservoir drainage as a simulation of the recession limb of karst spring hydrographs

Drainage of a cylindrical water-filled tank-reservoir has been analysed by different physical models, providing relative discharge-time equations. The process has been simulated (1) in a condition of free-flow discharge, where no energy is lost during the process, and (2) where friction forces and water viscosity take effect. Simulation (1) is considered to be a Torricelli reservoir, characterised by a linear decrease of discharge; (2) is based on Darcy’s law or on Poiseuille’s law, where discharge decreases exponentially with time, giving a straight line in the semilogarithm plot. For the Darcy’s law simulation, the tank tube was filled with sand. The cylindrical water-filled tank-reservoir drainage analysis has been applied to simulation of the actual shape of karst spring hydrographs. It has been determined that the recession coefficient, α, is proportional to a hydraulic constant, c, which represents the hydraulic characteristics during the baseflow recession, and α is inversely proportional to the product of the water-table area with the effective porosity. This product expresses the area of the aquifer filled by free-flowing water along the water table and can vary during the aquifer drainage.     

Performance evaluation of correction coefficients to optimize sediment rating curves on the basis of the Karkheh dam reservoir hydrography,west Iran

The prediction of useful lifetime of a dam is estimated through accurate estimate of river sediments which mostly depend on sediment rating curve. Over the past decades, various methods have been developed by investigators. With respect to the importance of this issue, in the present study, the best discharge-sediment relationship for Jelogir hydrometric station located at the upstream of Karkheh reservoir dam is presented. In the first step, sediment rating curves in annual, seasonal, monthly, wet and dry, and middle of the classes linear ways and applying 3 correction coefficients that include Smearing, FAO, and QMILE were obtained; then, their performance was evaluated. Comparison of these results with data obtained from hydrographical operation of Karkheh dam reservoir showed that the optimal equation of discharge-sediment at this hydrometric station follows annual linear sediment rating curve with QMILE correction coefficient. According to the results, annual method has estimated sediment volume less than the actual volume, about 98.7% of the actual sediment, while other evaluated methods have showed sediment volume more than the actual one, and among correction coefficients, the application of QMILE correction coefficient is more reasonable than other coefficients.     

广西灵水岩溶大泉水文地质条件

灵水泉为广西典型的构造型岩溶大泉,其泉域分布面积大,泉水具有出口多、流量大、动态较稳定等特点.近些年来,灵水泉出口流量呈现减少的趋势,而且水质也出现了轻微污染,引起当地政府的高度重视.为查明灵水泉含水介质特征与补给特性,综合采用地面调查、物探、钻探和地下水示踪等方法研究灵水泉岩溶管道分布特征,并圈定了灵水泉补给范围.研究成果表明:灵水泉上游岩溶管道结构为网络状,管道规模不大,呈带状集中分布;北部一带为该泉主要补给区,典型集中径流带长约8 km,宽200~700 m.根据同位素的高程效应,计算得出灵水泉补给高程为496 m,与圈出的补给范围高程相近,印证了调查结果.本研究可为制定灵水地下水资源的开发利用和保护方案提供依据.     

织金大龙井岩溶大泉形成机理研究

为了弄清大龙井岩溶大泉形成机理以及地下水补径排关系。通过调查大龙井地形地貌、补径排关系以及对水化学分析等研究大龙井岩溶大泉的形成机理,通过调查得知:大龙井岩溶大泉是形成于低山－丘陵地区的石灰岩地区。是山盆期和乌江期的强烈岩溶作用以及河谷的不断下切,加上上寨台地地表峰丛之间发育洼地、漏斗,中间区域的落水洞,大气降雨沿着落水洞进入地下,在重力作用下从南向北径流,在这过程中水流逐渐集中,岩溶空间形态也逐步扩大,最终水汇集于龙洞沟呈泉集中排泄出地面,形成大龙井岩溶大泉以及大龙井水系统。      

山西长治辛安泉域岩溶水硫酸盐污染来源分析

辛安泉域核心区域工农业相对发达,人类活动强烈,逐渐出现岩溶地下水位下降、泉流量减小和水质污染等水环境问题。硫酸盐污染是泉域岩溶水的主要污染物之一,通过科学手段进行污染来源分析和识别,可为泉域保护提供决策依据。硫氧同位素是地下水领域应用较广的一种环境同位素方法,不仅技术成熟且识别精度高。本次研究将硫氧同位素方法与水化学方法结合,在辛安泉域采取岩溶泉水、岩溶地下水、孔隙水、裂隙水和河水五类水样,测试硫同位素δ34S、氧同位素δ18O和硫酸根离子SO42-含量,以分析辛安泉域岩溶水硫酸盐污染来源。结果显示,辛安泉域岩溶水水质的硫酸盐大部分符合地下水III类标准,硫酸盐含量较高的区域主要集中在西部滞流缓流区与襄垣和长治子系统的分界处、长治子系统和平顺-壶关子系统南部等地区。西部滞流缓流区硫酸盐主要来源于石膏、硬石膏的溶蚀,人类活动影响较小。泉域南部岩溶水中硫酸盐主要来源是煤矿开采的影响,大气沉降也是重要来源之一。     

龙涧泉岩溶水系统特征

文章以地下水系统理论为指导,对龙涧泉岩溶水系统的边界条件、人工干预条件下地下水动力场演化特征等方面进行了系统的研究。根据区域地质、构造、地形地貌和水文地质条件,探究了龙涧泉岩溶水系统,圈定了系统的范围、边界性质、流动系统内部及其与外部系统之间的关系,确定龙涧泉为系统的唯一天然排泄口,龙涧泉岩溶水系统与白浪岩溶水系统无直接水力联系。龙涧泉岩溶水系统岩溶水补给来源主要是大气降水、河流入渗及侧向径流补给,现状条件下总补给量为864.42万m3/a,多年平均补给量为836.81万m3/a;排泄主要是水源地开采和矿山排水,现状开采量为4 117.2万m3/a。由于开采量大于允许开采量,并超过了总补给量,区内岩溶水一直处于超采状态。2004—2008年矿区岩溶水实测年均下降1.61 m/a,多年（1984—2008）水位平均降幅为5.68 m/a,最大降幅17.42 m/a。此外还讨论了岩溶水系统的补给、排泄条件,提出了龙涧泉岩溶水开发、保护、复泉与管理龙涧泉岩溶水系统的建议。      

平治河岩溶流域退水规律分析与降雨径流模拟

以平治河岩溶流域为研究对象,分析其地下退水规律,将其划分为9个子流域,在传统新安江模型基础上,将地下径流划分为慢速和快速地下径流,分别采用两个线性水库进行模拟,构建降雨-径流模拟方案,并选取2011-2015年期间的7场洪水作为率定期洪水,以确定性系数（DC）最大为优化目标,应用遗传算法率定模型参数,而以8场洪水作为验证期洪水进行验证分析,获得率定期合格率为85.71%,平均确定性系数为0.846,验证期合格率为75%,平均确定性系数为0.893,达到乙级精度。其结果表明所构建的模拟方案能够较好地模拟该流域的径流规律。      

聊城市东部岩溶地热田地下热水水化学特征及成因分析

通过对聊城市东部岩溶地热田的地下热水的化学成分、同位素及其水文地质特征的分析,对这一地区的地下热水的形成和演化过程进行了研究。结果显示地下热水的形成受区内深大断裂和基底构造的控制。本区地下热水的形成是在漫长的地质历史发展过程中各种自然因素综合作用的结果。δD和δ18O的关系及氚（T）值和水化学特征系数说明地下热水为近代大气降水入渗起源的中度或高度变质水,以40年前的古水占优势,新近入渗水的补给量较小。水化学成分的形成以溶滤、溶解作用为主,微量元素成分丰富,反映了地下水经过了漫长和复杂的径流及深循环过程。      

The impact of salt diapirs on the quality of carbonate karst waters,Bastak, Iran

The Gavbast karstic aquifer located in southern Iran is in direct contact with an exposed salt diapir. To assess the influence of the diapir on the quality of groundwater in the karstic aquifer, electrical conductivity, total dissolved solids, flow rate, temperature and major ion concentrations were measured at 57 sampling sites, including springs, surface waters and wells. A conceptual model of groundwater flow is proposed for the Gavbast karstic aquifer based on the geological setting, water budget, local base of erosion, and hydrochemistry of the sampling sites. The model suggests two subbasins in the Gavbast Anticline draining into two distinct discharging alluvial sections. Unexpectedly, groundwater discharging from the carbonate Gavbast aquifer is saline or brackish and water is of chloride type. The study indicates that the source of salinity of the Gavbast aquifers is infiltration of surface diapir-derived brine into the aquifer. The contribution of the diapir brine in the Gavbast karst aquifer is calculated about 4 L/s, using chloride mass balance. Construction of salt basins to evaporate brine discharging from the diapir springs is proposed to reduce the salinity of karst water. A row of strategically placed wells in the Gavbast karst aquifer would potentially exploit large volumes of fresh groundwater before it is contaminated by the salt. Such low-cost remediation should allow the agricultural exploitation of 40 km² of currently barren land.     

晋祠泉域岩溶水生态系统健康评价

文章尝试性地提出岩溶水生态系统的概念,从系统的特征、功能和面临的威胁三方面论述了其内涵,基于驱动力—压力—状态—影响—响应（DPSIR）模型,综合考虑自然因素和人类活动叠加影响,构建了岩溶水生态系统健康评价指标体系;用层次分析法（AHP）确定指标权重,用综合评价法确定岩溶水生态系统所处健康状态,并将其分为很健康、健康、亚健康、不健康和病态五级。并以晋祠泉域为例,采用ArcGIS空间分析技术确定岩溶水生态系统健康评价等级。结果表明： 泉域煤矿开采区处于不健康状态,东部平原区和中部径流区均处于亚健康状态,碳酸盐岩裸露区和汾河周边区域处于健康状态,分别占晋祠泉域总面积的29%、31%和40%。     

济南岩溶泉域地下水流模拟

为深入研究济南岩溶泉域地下水资源变化的现状及未来发展趋势,探索地下水资源可持续管理途径,文章建立了济南泉域地下水稳定流和非稳定流模拟模型,分析了地下水流场及泉水流量变化趋势,并圈划了泉群地下水汇流带。在泉群汇流带内开采地下水直接影响泉流量,而水源地开采通过影响泉群汇流带间接影响泉流量。泉流量呈明显的季节性变化,且与降水量紧密相关:丰水期水位升高,泉流量增加;枯水期水位降低,泉流量减少。保护天然补给量与增加人工补给量是保证泉水长流的重要措施。     

Influence of precipitation on bacterial structure in a typical karst spring,SW China

Micro-organisms are major components in the environment, which play a key role in groundwater environment. This study aims to investigate the bacterial diversity over time in a typical karst spring named S31 and its response to hydrogeochemical parameters. Quantitative PCR and 16S rRNA high-throughput sequencing was adopted to detect changes of the bacterial community structure. For the correlations between hydrogeochemical parameters and predominant phyla, redundancy analysis were adopted. According to the results, hydrochemical characteristics were controlled by carbonate equilibrium system and dynamic groundwater transformation which was influenced distinctly by precipitation. In addition, the redundancy analysis indicates that HCO_3~-, Ca~(2+), Eh, temperature and cumulative precipitation are the most important hydrogeochemical and environmental parameters to determine the bacterial community structures. That is to say, temperature can influence bacterial abundance by controlling dissolved oxygen content. Precipitation is another important factor which determines the community composition and bacterial structure directly or indirectly. Moreover, acidobacteria, proteobacteria, and bacteroidetes play key roles in response to the environmental factors in the groundwater of karst zones.     

Synoptic analysis of unexampled super-heavy rainfall on April 1, 2019, in west of Iran

Natural Hazards - The aim of this study is to analyze the synoptic and analyzing the mechanisms of flood occurrence on April 1, 2019, in the western half of Iran. In order to statistically analyze...     

Experimental vulnerability curves for the residential buildings of Iran

Iran is one of the most seismically active countries of the world located on the Alpine-Himalayan earthquake belt. More than 180,000 people were killed due to earthquakes in Iran during the last five decades. Considering the fact that most Iranians live in masonry and non-engineered houses, having a comprehensive program for decreasing the vulnerability of society holds considerable importance. For this reason, loss estimation should be done before an earthquake strikes to prepare proper information for designing and selection of emergency plans and the retrofitting strategies prior to occurrence of earthquake. The loss estimation process consists of two principal steps of hazard analysis and vulnerability assessment. After identifying the earthquake hazard, the first step is to evaluate the vulnerability of residential buildings and lifelines and also the social and economic impacts of the earthquake scenarios. Among these, residential buildings have specific importance, because their destruction will disturb the daily life and result in casualties. Consequently, the vulnerability assessment of the buildings in Iran is important to identify the weak points in the built environment structure. The aim of this research is to prepare vulnerability curves for the residential buildings of Iran to provide a proper base for estimating probable damage features by future earthquakes. The estimation may contribute fundamentally for better seismic performance of Iranian societies. After a brief review of the vulnerability assessment methods in Iran and other countries, through the use of the European Macroseismic method, a model for evaluating the vulnerability of the Iranian buildings is proposed. This method allows the vulnerability assessment for numerous sets of buildings by defining the vulnerability curves for each building type based on the damage observations of previous earthquakes. For defining the vulnerability curves, a building typology classification is presented in this article, which is representative of Iranian building characteristics. The hazard is described in terms of the macroseismic intensity and the EMS-98 damage grades have been considered for classifying the physical damage to the buildings. The calculated vulnerability indexes and vulnerability curves show that for engineered houses there is not any notable difference between the vulnerability of Iranian and Risk-UE building types. For the non-engineered houses, the vulnerability index of brick and steel structures is less than the corresponding values of the other unreinforced masonry buildings of Iran. The vulnerability index of unreinforced and masonry buildings of Iran are larger than the values of the similar types in Risk-UE and so the Iranian buildings are more vulnerable in this regard.     

Recharge rate estimation in the Mountain karst aquifer system of Figeh spring, Syria

Figeh watershed spring is one of the important groundwater aquifer, which is considered a major source for drinking waters of Damascus city and countryside. The origin identification and recharge estimates of groundwater are significant components of sustainable groundwater development in this Mountain karst aquifer of Figeh spring. During the period 2001–2009, monthly groundwater and precipitation samples were taken and the isotopic compositions of δ¹⁸O, δ²H, and chloride contents were analyzed to identify groundwater origins and to estimate recharge rates. The δ¹⁸O, δ²H of the groundwater show that the groundwater recharge is of meteoric origin. The chloride mass balance (CMB) method was used to quantify recharge rates of groundwater in the Mountain karst aquifer of Figeh spring. The recharge rate varies from 192 to 826 mm/year, which corresponds to 43 and 67% of the total annual rainfall. Recharge rates estimated by CMB were compared with values obtained from other methods and were found to be in good agreement. This study can be used to develop effective programs for groundwater management and development.     

济南泉域排泄区岩溶地下水水化学特征

文章通过分析研究济南泉域排泄区地下水水化学成分特征及形成过程,结合岩溶地下水的补径排条件,揭示了不同位置、不同深度循环的水质存在差异的原因。为保护泉水、优化泉域内地下水的开采方案提供了依据。     

喀斯特流域枯季径流衰减系数与地表形态特征相关分析研究

针对喀斯特流域地形、地貌对枯季径流的调蓄作用,选用乌江流域思南站以上19个水文站点枯季流量资料进行枯季径流衰减规律分析。根据枯季径流衰减曲线的拟合将枯季径流分为快速裂隙流和慢速裂隙流两段退水过程,并计算相应的衰减系数。通过对衰减系数与流域地表形态特征的单因素和多因素回归分析,确定影响衰减系数的主要影响因子为高程特征值和地形指数特征值,并建立两者与衰减系数的二元非线性回归方程(a1=0.781-0.266?ln(x)+0.633?ln(y),a2=0.061-0.016?ln(x)+0.044?ln(y)),其置信区间都大于99%,说明曲线整体拟合显著,为枯期径流衰减系数区域化分析及无/缺资料流域的水文模拟提供基础。      

Seismic hazard assessment of the city of Hamedan and its vicinity, west of Iran

This article presents the results of deterministic and probabilistic seismic hazard analyses (DSHA and PSHA) of the city of Hamedan and its neighboring regions. This historical city is one of the developing cities located in the west of Iran. For this reason, the DSHA and PSHA approaches have been used for the assessment of seismic hazards and earthquake risk evaluation. To this purpose, analyses have been carried out considering the historic and instrumented earthquakes, geologic and seismotectonic parameters of the region covering a radius of 100?km, keeping Hamedan as the center. Therefore, in this research, we studied the main faults and fault zones in the study area and calculated the length and distance of faults from the center of Hamedan. In the next step, we measured the maximum credible earthquake (MCE) and peak ground acceleration (PGA) using both DSHA and PSHA approaches and utilized the various equations introduced by different researchers for this purpose. The results of DSHA approach show that the MCE-evaluated value is 7.2 Richter, which might be created by Nahavand fault activities in this region. The PGA value of 0.56?g will be obtained from Keshin fault. The results of PSHA approach show that the MCE-evaluated value is 7.6 Richter for a 0.64 probability in a 50-year period. The PGA value of 0.45?g will be obtained from Keshin fault. Seismic hazard parameters have been evaluated considering the available earthquake data using Gutenberg?CRichter relationship method. The ??a?? and ??b?? parameters were estimated 5.53 and 0.68, respectively.     

Environmental characterization of a karst polje: an example from Izeh polje,southwest Iran

Groundwater contamination is a well-known phenomenon, which occurs on local and regional scales in Izeh polje. The aims of this paper are investigation of the impact of human activities on the polje ecosystem, determination of the vulnerability of ground water, and to solve environmental problems. Nitrate contamination of groundwater in the Izeh polje was predicted using a solute transport model. The nitrate concentration in groundwater in most parts of Izeh polje is greater than maximum concentration permissible for drinking water, i.e., 45 mg/l. The main source of nitrate in the eastern underground areas of Izeh city is the domestic sewage. Bacterial pollution of shallow ground water in Izeh polje is severe and widespread. About 45% of ground water samples in May and September 2001 have positive MPN coliforms. Infiltration of polluted surface waters and decrease of water table depth, have lead to bacterial pollution of 80% of ground water samples in January 2002. The northeast, south and southwest areas of Izeh polje have higher pollution potential rather than its middle parts. The aquifer vulnerability indices in the middle, eastern, and northern parts of the polje are moderately lower as a result of decreased sediment size of the aquifer. The pollution in the polje depends on the amount and presence of pollutants. If they do exist, the possibility of pollution is considerable due to the coarseness of materials and shallow depth of groundwater table.