Incorporating Reservoir Transfer into Treatment Optimization Decisions

The Massachusetts Water Resources Authority (MWRA) supplies unfiltered water from two large surface water reservoirs to the metropolitan Boston area, as well as to three smaller communities in central Massachusetts [the Chicopee Valley Aqueduct (CVA) communities]. Quabbin Reservoir is larger than Wachusett Reservoir, and has traditionally been used to supplement the Wachusett during the summer period. Quabbin water is also of better quality, with lower reactive natural organic matter (NOM). The MWRA began to add chlorine at Wachusett in 1997, and a new facility for adding chlorine at Quabbin for the CVA was also started up in 2000 to meet primary disinfection regulations to meet pathogen inactivation. The reaction of chlorine with NOM produces undesirable disinfection by-products (DBPs). The absorption of ultraviolet light at a wavelength of 254 nm was identified in chlorine decay studies to be the most important raw water quality parameter for predicting chlorine decay and DBP formation. This technical note summarizes the chlorine decay model for Wachusett and Quabbin water. The model is extended to ozonation of Wachusett water for the future Walnut Hill treatment plant. The models allowed the development of a trigger using UV-254 to time the Quabbin transfer to optimize treatment results. It is believed that the model for disinfectant decay and the use of UV-254 as a trigger for water treatment decisions are generalized and applicable to other water utilities.     

川南碳酸盐岩缝洞中隐蔽性天然气储量早期预测——“排水找气”井储量早期估算探讨

关于封闭性碳酸盐岩缝洞气藏天然气储量计算，已有公认的经典计算公式，而探讨缝洞性碳酸盐岩产水圈闭中隐蔽性天然气储量的预测和计算，尚属近年提出的新课题。根据物质平衡原理，推导了这类隐蔽性天然气储量计算公式，并提出“折算气量”新概念，建立气水同产井Ｐ／Ｚ—∑Ｇｐ关系压降图。运用该压降图，也可早期预测产水井中隐蔽性天然气储量。通过Ｈ１６井储量计算实例，得到了证实。     

我国水库大坝安全与管理的实践和面临的挑战

目前我国的大坝安全与管理已经取得较大进展,水平也有较大提高.但在新世纪依然面临着严峻挑战,我国病险水库除险任重道远;制度化、法规化、科学化的管理体制有待建设完善;面广量大的小型水库的安全问题已经成为防洪保安体系中最薄弱的环节,亟待解决;专业技术人员的数量和素质有待提高;水库大坝风险管理技术、除险综合优化技术、小型水库大坝评价和加固技术、除险效果的评价技术等安全与管理技术需要加强研究.因此,建议加速业主制度建设和区域性安全管理模式的探索、进一步加强法规建设、加强国际合作、引进和推广先进管理模式.     

Reservoir Bank Deformation Modeling: Application to Grangent Reservoir

Within inshore or fluvial environments, submerged fine matter mud banks are characterized by a high water content, a great spatial variability, and a strong deformability. The study of their instabilities induced by the variation of hydraulic stress requires a coupled modeling of sliding, erosion, and deposition mechanisms. In order to predict the impact of dam reservoir emptying on the stability of immersed upstream slopes, the method of approach to the problem proposed here combines theoretical developments, numerical modeling, site observations, and measurements. First, the theoretically achieved sliding criterion is compared with unstable mud height measurements. For more accuracy in the representation of the natural events, the sliding criterion is then integrated within a numerical code which couples the computation of hydrodynamic conditions, the erosion, and deposition of mud and the banks sliding. Finally, the results of the combination of all these mechanisms are compared with the variations in the bathymetric profiles obtained on the experimental site.     

Comparison of Long-Term Observed Sediment Trap Efficiency with Empirical Equations for Coralville Reservoir, Iowa

Trapping efficiency (TE) is defined as the percent of particles that are retained within an impoundment. TE can vary from ? 0% indicating no sediment is retained or is lost, to 100% where all the sediment is retained. In this paper a high quality, long-term data set (32?years) was used to demonstrate that annual sediment trap efficiencies for a run of the river impoundment are variable. For water years 1973–2005, annual trap efficiencies for Coralville Reservoir ranged from 5.6 to 95.8%, with a mean of 74.7% and a median of 79.9%. Overall trap efficiency for the entire period was determined to be 80.3% and a detention time of 12.4?days. A comparison of the observed long-term TE was done against different empirical TE equations that are commonly used (Brown, Brune, Churchill, Dendy, Heinemann, & USDA/Summit Co., Water District). The Churchill equation provided the best fit of the empirical trap efficiency equations (TEC = 79.1%); all other empirical TE relationships underestimated the observed trap efficiency with errors ranging from 13.7 to 33.1%. Bathymetric data show that since 1958 the reservoir has lost 11% of its flood storage capacity, and over 62% of its normal pool capacity. For the time studied (1973–2005) the loss of storage is estimated to correspond to 16.9×109?kg of sediment deposited in the reservoir, resulting in an annual sedimentation rate of 5.3×108?kg?year?1.     

Coupling an Underflow Model to a Three-Dimensional Hydrodynamic Model

A separate underflow model is coupled to the three-dimensional (3D) estuary and lake computer model. The underflow equations are solved on a two-dimensional (2D) grid underlying the 3D model grid. The underflow model entrains ambient water whose properties are given by the fluid properties of the bottom boundary cells in the 3D model. This new approach allows improved representation of underflow effects in z-coordinate models by reducing numerical convective entrainment. An idealized case is used to illustrate the benefits of the underflow model. Comparisons of model results and field data for a saline underflow event in Lake Ogawara and a cold-water underflow in Lake Kinneret demonstrate improved model capability in representing underflow events that are thin compared to the vertical grid scale.     

Reducing Numerical Diffusion Effects with Pycnocline Filter

Numerical or artificial diffusion is the unintentional smoothing of gradients associated with the discretization of the transport equations. In lakes and reservoirs where through-flow is small, the effects of numerical diffusion of mass are cumulative, leading to a progressive weakening of vertical density stratification. This density field misrepresentation precludes accurate, long-term, three-dimensional (3D), hydrodynamic simulations on fixed grids in closed basins with an active thermocline. An ad hoc technique to limit the destratifying effects of numerical diffusion of mass is presented and tested for a 3D, hydrostatic, Z-coordinate numerical model. The technique quantifies the domain-integrated numerical diffusion by assessing the change in the background potential energy Eb. At each time step, the change in Eb associated with numerical diffusion is calculated, then removed using a sharpening filter applied to each water column. In idealized test cases, the filtering technique is effective in maintaining density stratification over one year while undergoing periodic, large-amplitude forcing by internal waves. Forty-day simulations of Lake Kinneret compared to field measurements demonstrate improved representation of density stratification using the filtering technique.     

安塞油田坪北区低渗透油藏复合解堵技术研究

由于坪北油田储层物性差,孔隙度低,渗透率低,主要属于小孔细喉道,开采过程中很容易受到伤害,并造成油井近井地层的堵塞,从而使油井在措施后的较短时间内产量下滑。从地层堵塞的原因入手,综合考虑影响地层堵塞的各种因素采用合理的酸化解堵工艺,取得较好的现场应用效果。