Efficient uncertainty quantification techniques in inverse problems for Richards’ equation using coarse-scale simulation models

This paper concerns efficient uncertainty quantification techniques in inverse problems for Richards’ equation which use coarse-scale simulation models. We consider the problem of determining saturated hydraulic conductivity fields conditioned to some integrated response. We use a stochastic parameterization of the saturated hydraulic conductivity and sample using Markov chain Monte Carlo methods (MCMC). The main advantage of the method presented in this paper is the use of multiscale methods within an MCMC method based on Langevin diffusion. Additionally, we discuss techniques to combine multiscale methods with stochastic solution techniques, specifically sparse grid collocation methods. We show that the proposed algorithms dramatically reduce the computational cost associated with traditional Langevin MCMC methods while providing similar sampling performance.     

Measurement of streambed hydraulic conductivity and its anisotropy

 A method is described for the measurement of streambed hydraulic conductivity. Unlike permeameter methods, this method applies straight and l-shaped standpipes directly to streambeds for measurements of in-situ hydraulic conductivity in the vertical (K _v ) and horizontal (K _h ) directions, as well as in other oblique directions (K _s ). This method has advantages in determination of K _v values over grain-size analysis, permeameter tests, or slug test methods. Also unique to this method is that it provides K _s values of a streambed. The measured results can be used to construct a hydraulic conductivity ellipse and to evaluate the anisotropy of streambed sediments. Field examples from the Republican River, Nebraska, demonstrated the usefulness of this method in the determination of streambed hydraulic conductivity and anisotropy along or across a river channel. Results indicate that the K _h is about three to four times larger than K _v , whereas K _s values are larger than K _v but smaller than K _h . Received: 6 March 2000 · Accepted: 18 April 2000     

Simultaneous transport of water and solutes under transient unsaturated flow conditions — A case study

The imbalance between incoming and outgoing salt causes salinization of soils and sub-soils that result in increasing the salinity of stream-flows and agriculture land. This salinization is a serious environmental hazard particularly in semi-arid and arid lands. In order to estimate the magnitude of the hazard posed by salinity, it is important to understand and identify the processes that control salt movement from the soil surface through the root zone to the ground water and stream flows. In the present study, Malaprabha sub-basin (up to dam site) has been selected which has two distinct climatic zones, sub-humid (upstream of Khanapur) and semi-arid region (downstream of Khanapur). In the upstream, both surface and ground waters are used for irrigation, whereas in the downstream mostly groundwater is used. Both soils and ground waters are more saline in downstream parts of the study area. In this study we characterized the soil salinity and groundwater quality in both areas. An attempt is also made to model the distribution of potassium concentration in the soil profile in response to varying irrigation conditions using the SWIM (Soil-Water Infiltration and Movement) model. Fair agreement was obtained between predicted and measured results indicating the applicability of the model.     

Key Groundwater Control Factors of Deep Buried Coalfield by Landform and Sedimentation in the Northern Ordos Basin

There were three landforms (i.e. desert, bedrock platform and loess gully) in deep-buried coalfield of northern Ordos Basin. Water inflow of working face in desert area was 1~2 orders of magnitude larger than that in other landform areas. In order to find out the key controlling factors of the directly water filled aquifers on the roof of the coal seam, we carried out research from the aspects of topography, landform and geological sedimentation. The results showed that desert landform provides abundant recharge water for underlying aquifers because of gentle topography, large precipitation infiltration coefficient, thick and water-rich quaternary system. While bedrock platform and loess gully landform were the water sources with weak recharge capacity of underlying aquifers. The sandstone-mudstone interbedding structure formed by continental deposits resulted in the absence of regional stable aquifers in Jurassic and Cretaceous strata on the roof of coal seams. Pumping tests of boreholes showed that all strata belong to weak to medium water-rich aquifers. The groundwater level of Cretaceous aquifer decreased by 20~130 m in three mines. There was a close hydraulic relationship between shallow and deep aquifers. The Mesozoic strata belonged to fluvial deposits. Qilizhen sandstone and Zhenwudong sandstone aquifers were mainly developed on the roof of the coal seam, which were characterized by thick medium-coarse sandstone sections. The geological and sedimentary conditions of direct water-filled aquifer were similar, but the amount of borehole water, cumulative pre-drainage water and water inflow from goaf in desert geomorphic area were much larger than those in bedrock platform and loess gully geomorphic area. The water-rich of the aquifer was mainly controlled by geomorphology, and the water sources of the deep aquifers were meteoric precipitation and Quaternary aquifer. In different mines with similar Quaternary conditions in Mu Us Desert, there were also great differences in the amount of borehole water, cumulative pre-drainage water and water inflow from goafs. The difference was related to the thickness and lithology of the aquifers. It reflected that the geological sedimentary conditions of the coal seam roof were also important factors to control the water-rich of the aquifers. Topography, landform and geological sedimentation were the key factors to control the water-rich of the aquifer directly and the water inflow from the working face.     

气举反循环钻进井壁稳定及适用性探讨

气举反循环工艺具有钻进效率高、携带岩屑能力强、防漏效果好以及钻头寿命长等优点,同时还可以提高流体矿产的产能。但是一般认为气举反循环钻进抽吸作用会产生负压,不利于井壁稳定,不宜在松散地层应用。本文通过计算气举反循环钻进环空水力参数,并从环空压力以及冲洗液流态、流速等方面探讨研究气举反循环钻进中井壁稳定及其适用性,指出通过选取合适的钻具组合以及调节冲洗液性能,可使气举反循环工艺对不同地层的适应性更广。     

气举技术应用于深海无隔水管泥浆回收钻井工艺可行性分析

无隔水管泥浆回收钻井技术作为新兴钻井技术,具有安全环保、简化井身结构和降低钻探风险等优点。传统的无隔水管泥浆回收钻井技术依靠水下泵将海底井口泥浆举升至甲板面,该方式对水下泵的举升能力及可靠性要求极高。未来深海钻井领域,水下泵将会是限制无隔水管泥浆回收钻井技术应用的“瓶颈”。本文借鉴陆地气举反循环钻井原理,利用气举技术部分或完全替代水下泵,分别从设备技术现状、流量可调性、适用环境、井控安全等方面探究气举用于无隔水管泥浆回收技术的可行性。结果表明,气举反循环技术及相关设备性能满足无隔水管泥浆回收的使用要求,而且具有上返流量可调、安全等特点,有较高的研究应用价值。     

地窝堡机场东南大风特征及其大气结构

按照民航系统气象行业标准要求,结合乌鲁木齐国际机场的具体情况,给出乌鲁木齐机场东南大风的定义,并应用乌鲁木齐机场1978~2012年间逐时观测的风速风向对机场东南大风的特征进行分析,然后再引入水跃理论和Froude数,对机场东南大风发生时的大气结构做解析。结果表明:(1)1980年代与2000年代至今,为东南大风的兴盛期,1990年代为东南大风的低值期;(2)东南大风主要集中出现在春秋季,其中尤以4月出现次数最多,占总出现次数的36.4%;(3)早晨至中午期间,东南大风多发且风速较大;午后至夜间,东南大风发生次数少,且风速也相对较小;(4)东南大风的持续时间以低于5 h为主,其次为持续11 h以上的大风,而持续时间在5~11 h之间的大风出现最少;(5)对于4月和11月而言,大风发生时达坂城与本场的气压差与同时次本场的温度垂直递减率存在显著的线性关系。     

水工程建设对长江流域鱼类生物多样性的影响及其对策

长江流域鱼类种类丰富、资源量大、特有性高、经济种类多,其生物多样性具有重要的生态价值、经济价值和科学价值．流域内鱼类生物多样性由于面临河流梯级开发引起的洄游阻隔、生境破碎和水文情势等改变的严重威胁,种群下降趋势明显．为保护长江流域鱼类生物多样性,有必要更新水工程规划理念和设计技术,修建鱼道等必要过鱼设施,进行水库生态调度,建立鱼类自然保护区和建立生态补偿机制等．     

Hydraulic and salinity regime of two affected sites in the Yizre'el valley,Israel

Causes of recent salinization of numerous plots in the Yizre'el Valley of Israel were examined through a detailed field study of two severely affected sites. in particular, the theory of artesian influence on salt build-up in the upper cultivated soil layer was investigated. Two piezometer nests and 12 wells were installed to study the subsurface hydraulic regime. Water samples and soil extracts were taken to characterize the chemical composition down to 10m. No significant head differences were measured at the lower site, while at the upper site 96 per cent of the head that existed at the deep (7.5 m) artesian layer was dissipated within the overlying thick clay layer. Slight head differences were noted in the shallow layers. the deep-lying, coarse-textured aquifer differs markedly from the upper confining layers and constitutes an independent water body that has little relevance to surface processes. Chemical and hydrological analyses indicate that applied low-quality irrigation waters May, be the primary cause of downward-moving salinity and alkalinity which, in turn, affect soil permeability and site productivity.