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The COVID-19 pandemic has tested many aspects of society, but has also reminded us anew of the limitations and challenges of our scientific approaches. Take the example of randomized trials. [...]

Land subsidence caused by the excessive use of groundwater resources has traditionally caused serious and costly damage to the Los Banos-Kettleman City area of California's San Joaquin Valley. Although the arrival of surface water from the Central Valley Project has reduced subsidence in recent decades, the growing instability of surface water supplies has refocused attention on the future of land subsidence in the region. This report develops a three-dimenslonal, numerical simulation model for both groundwater flow and land subsidence. The simulation model is calibrated using observed data from 1972 to 1998. A probable future drought scenario is used to consider the effect on land subsidence of three management alternatives over the next thirty years. Maintaining present practices virtually eliminates unrecoverable land subsidence, but with a growing urban population to the south and concern over the ecological implications of water exportation from the north, it does not appear that the delivery of surface water can be sustained at current levels. The two other proposed management alternatives reduce the dependency on surface water by increasing groundwater withdrawl. Land subsidence is confined to tolerable levels in the more moderate of these proposals, while the more aggressive produces significant long-term subsidence. Finally, an optimization model is formulated to determine maximum groundwater withdrawl from nine water sub-basins without causing irrecoverable subsidence over the forecasted period. The optimization reveals that withdrawl of groundwater supplies can be increased in certain areas in the eastern side of the study area without causing significant subsidence.

El envejecimiento de la población y la creciente carga de enfermedades crónicas con el consiguiente aumento de morbilidad que originan, constituyen hoy en día un reto para los sistemas sanitarios. Para hacer frente a esta nueva realidad demográfica, la Organización Mundial de la Salud (OMS) ha destacado la necesidad de transformar los sistemas de salud con el fin de pasar de los modelos curativos centrados en las enfermedades a una atención integrada y centrada en el paciente1. La atención integrada es un principio que busca mejorar los resultados de salud mediante la integración de los procesos asistenciales. Se trata, en definitiva, de dar coherencia y buscar sinergias entre los diferentes niveles del sistema sanitario para lograr que los cuidados sanitarios sean menos fragmentados, más coordinados y más eficientes, y en definitiva, de mayor calidad2. El Institute of Medicine (IOM) define en 2001 la calidad asistencial como el grado por el que los servicios asistenciales incrementan la posibilidad de resultados de salud deseados para individuos y poblaciones, en concordancia con el conocimiento profesional actual. Las dimensiones esenciales de la calidad incluyen efectividad, eficiencia, equidad, accesibilidad, atención centrada en el paciente y seguridad3. El informe Order for Chaos emitido por la National Patient Safety Foundation (NPSF) concluye que una deficiente integración de la asistencia está vinculada a un mayor número de eventos adversos, por lo que las mejoras en esta área deben encontrarse entre las principales prioridades para lograr un sistema sanitario seguro, efectivo y eficiente4. Asimismo, destacan como aspectos para seguir avanzando en la mejora de la seguridad del paciente la necesidad de trabajar en equipos multidisciplinares integrados, el fomento de la participación del paciente como verdadero socio en todos los aspectos de la atención y la creación de entornos laborales seguros. Osakidetza ha trabajado durante años en la búsqueda del máximo nivel de seguridad clínica para sus pacientes. La seguridad constituye una prioridad para el Departamento de Salud y es uno de los objetivos recogidos tanto en el Plan de Salud 2013-2020 como en los Retos y Proyectos Estratégicos de Osakidetza 2017-2020. El primer documento que recogía las diferentes líneas de acción corporativas se elaboró en el año 2013 con el fin de convertir la seguridad en uno de los pilares de la asistencia sanitaria, contribuyendo al mantenimiento de la cultura de seguridad. Con la Estrategia de Seguridad 20 20 se pretende garantizar la continuidad de líneas de acción, respaldando el aprendizaje de los últimos años y asumiendo nuevos retos, que buscan promover una cultura de seguridad integral, consolidar el modelo de participación de los profesionales y potenciar la comunicación y coordinación asistencial, cada vez más necesarias en un sistema sanitario complejo como el nuestro. Por todo ello, un enfoque integrado en base a los sistemas necesarios para asegurar la seguridad del paciente también ayudará a garantizar la calidad de la asistencia5, de ahí que constituya un tema prioritario a nivel mundial pese a los esfuerzos realizados y las mejoras implantadas.

Land subsidence caused by the excessive use of ground water resources has traditionally caused serious and costly damage to the Los Banos-Kettleman City area of California's San Joaquin Valley. Although the arrival of surface water from the Central Valley Project has reduced subsidence in recent decades, the growing instability of surface water supplies has refocused attention on the future of land subsidence in the region. This report develops a three dimensional, numerical simulation model for both ground water flow and land subsidence. The simulation model is calibrated using observed data from 1972 to 1998. A probable future drought scenario is used to consider the effect on land subsidence of three management alternatives over the next thirty years. Maintaining present practices virtually eliminates unrecoverable land subsidence, but with a growing urban population to the south and concern over the ecological implications of water exportation from the north, it does not appear that the delivery of surface water can be sustained at current levels. The two other proposed management alternatives reduce the dependency on surface water by increasing ground water withdrawal. Land subsidence is confined to tolerable levels in the more moderate of these proposals, while the more aggressive produces significant long-term subsidence. Finally, an optimization model is formulated to determine maximum ground water withdrawal from nine water sub-basins without causing irrecoverable subsidence over the forecasted period. The optimization reveals that withdrawal of ground water supplies can be increased in certain areas in the eastern side of the study area without causing significant subsidence.

Two management models are developed to determine the optimal operating policies for hydraulically connected time-variant surface and ground water supplies in a hypothetical system. The system involves a multipurpose reservoir, a hydraulically connected stream and aquifer, agricultural plot, water supply and observation wells, and an artificial recharge zone so as to address various hydrologic components experienced in Yolo County in the management models. The first model minimizes deviations from a set of rule curves defined for storage in the reservoir and along stream course so as to consider possibilities for storage excess water in wet periods and its distribution in subsequent dry periods. The second model, in addition to the objective of the first model, minimizes total operational costs of surface and subsurface water storages (pricing) while meeting the target storage levels in the surface water supplies. The first model is formulated as a linear programming model whereas the second one is formulated as a nonlinear programming model and a []-form approximating model is employed in the solution phase.The hypothetical system is divided into components which are subsequently integrated using numerically-generated response functions that relate the system's behavior to various system excitations. The management model is formulated and solved for monthly time steps, which include both dry and wet conditions, to determine reservoir release, pumpage rate from supply wells, artificial recharge rate, water diversion from reservoir and stream to the demand area, and storage both in the reservoir and along the stream course at an optimal level in each time step over a six-month planning horizon. Sensitivity analysis of the first management plan with respect to potential use of groundwater supplies is performed to analyze the latter's impact on the operating policies. Furthermore, the performance of the []-form approximating model for conjunctive management models applied to the hypothetical system is found to be promising.

The effort that led to this report is twofold. First, it deals with the development of fundamental transport equations and their solutions; they describe the effect of low-permeability zones on the motion and spread of contaminant plumes in high-permeability porous layers. Second, it concerns the development of an analytical multi phase-transport model that describes leaching of pesticides in soils and their fate and transport in groundwater. Using Monte Carlo simulations, the effect of stochastic precipitation, random adsorption, and random (bio )chemical reaction, on the probability distributions of the herbicide Simazine, is investigated under conditions typical to the City of Fresno in California.The transport equations that are developed in Chapter 2 describe the capacitance of low permeability layers to store and release reactive constituents by diffusion and mechanical mixing. It is shown that under quasi-steady conditions and a mean flow parallel to the bedding, lateral solute transfer between thin layers is governed by the phenomenological first-order rate model, with a uniquely defined mass transfer rate coefficient, modified to account for reactive constituents. Two-dimensional analytical solutions are obtained in Chapter 3 for the first-order rate model in an infinite porous medium, using the methods of Fourier and Laplace transforms. and superposition. The solutions consider a rectangular area at the source with (l) an instantaneous release of a contaminant mass, and (2) an exponentially-decaying source concentration, applied at a fixed rate. Comparison of the theory with tracer chloride levels at the Borden aquifer indicates that the first-order rate model can describe adequately the dispersion process, on the basis of lateral or transverse diffusive mass transfer between layers.In the second effort (Chapter 4), a multiphase transport model is developed with the objective of investigating the impact of soil environment, physical and (bio )chemical processes, especially, volatilization, crop uptake, and agricultural practices on long-term vulnerability of groundwater to contamination by pesticides. The soil is separated into root and intermediate vadose zones, each with uniform properties. Transport in each soil zone is modeled on the basis of complete mixing, by spatial averaging the related point multi phase-transport partial differential equation (i.e., linear-reservoir models). Transport in the aquifer, however, is modeled by a two-dimensional advection-dispersion transport equation, considering adsorption and firstorder decay rate. Vaporization in the soil is accounted for by assuming liquid-vapor phase partitioning using Henry's law, and vapor flux (volatilization) from the soil surface is modeled by diffusion through an air boundary layer. Sorption of liquid-phase solutes by crops is described by a linear relationship that is valid for first-order (passive) crop uptake. The model is applied to five pesticides (Atrazine, Brornacil, Chlordane, Heptachlor, and Lindane), and the potential for pesticides contamination of groundwater is investigated for sandy and clayey soils. Simulation results show that groundwater contamination can be substantially reduced for clayey soil environments, where bio(chemical) degradation and volatilization are most efficient as natural loss pathways for the pesticides. Also, uptake by crops can be a significant mechanism for attenuating exposure levels in groundwater, especially in a sandy soil environment and for relatively persisting pesticides. Further, simulations indicate that changing agricultural practices can have a profound effect on vulnerability of groundwater to mobile and relatively persisting pesticides.The deterministic model is integrated with the Monte Carlo method in Chapter 5, to obtain the probability density function, mean, and standard deviation of the concentrations in groundwater, due to random adsorption and stochastic precipitation. The distribution coefficient, which is used to calculate the retardation factor for equilibrium adsorption, is assumed to be normally distributed, and the precipitation is modeled by fitting an ARIMA model to an observed time series. Consequently, the results of the analysis are also probability distribution functions for the concentration of the contaminant. which are useful representations for regulation and management purposes. The stochastic model is applied to data typical to the Fresno area in California, to assess the impact of herbicide Simazine on groundwater quality. The results show that predicted concentrations exhibit non-Gaussian probability distributions and standard deviations of the order of magnitude of the estimated means. Further, predictions made on the basis of averaged values of input parameters may substantially overestimate in transient, and later underestimate, the actual mean (ensemble) of the contaminant levels in groundwater. The results also highlight the importance of accounting for the mechanism of preferential flow.

Starting with a stochastic differential equation with random coefficients describing steady-stale flow, the effective hydraulic conductivity of 1-, 2-, and 3-dimensional aquifers is derived. The natural logarithm of hydraulic conductivity (lnK) is assumed to be heterogeneous, with a spatial trend, and Isotropic. The effective conductivity relates the mean specific discharge in an aquifer to the mean hydraulic gradient, thus its importance in predicting Darcian discharge when field data represent mean or average values of conductivity or hydraulic head. Effective conductivity results are presented in exact form in terms of elementary functions after the introduction of special sets of coordinate transformations in two and three dimensions. It was determined that in one, two, and three dimensions, for the type of aquifer heterogeneity considered, the effective hydraulic conductivity depends on: (i) the angle between ihe gradient of the trend of lnK and the mean hydraulic gradient (which is zero in the one-dimensional situation): (2) (inversely) on the product of the magnitude of the trend gradient of lnK, b, and the correlation scale of InK, λ; and (3) (proportionally) on the variance of lnK, σ12. The product bλ plays a central role in the stability of the results for effective hydraulic conductivity. 1996 International Association for Mathematical Geology.

A methodology for the restoration and cleanup of existing subsurface contaminated sites and for the containment of pollutants is developed. The remediation problem is posed as an optimization model where the rates and locations of pumping and injections are to be determined given the characteristics and extent of the contamination plume. The solution of the remediation problem is based on the econometric method of feedback control coupled with ground water flow and transport simulations. For site characterization and monitoring of the contaminant distribution and extent, an optimal sampling methodology is presented. The sampling design is based on geostatistical methods and yields optimal estimation of the subsurface parameters and pollutant concentrations, therefore providing informed decision-making for ground water remediation and contaminant removal. The remediation plan is optimized so as to lower the contamination level to a pre-specified level by the end of the remediation period while minimizing the cost of pumping and treatment The objective function of the optimal feedback control model consists of a successive minimization of a weighted sum of squared deviations of the achieved cleanup level at each stage from the desired target level of ground water quality.

A network design approach developed in this paper identifies monitoring sites in multi-layered, regional ground water flow systems at risk of contamination from waste storage facilities. Candidate locations are assigned weights that quantify monitoring value in terms of the prospect of plume detection and exposure hazard criteria. Detection criteria are based on the location of a site with respect to the source of contamination and potential contaminant plumes. Exposure criteria are based on the size of the population that consumes water from a supply well and the distances between the supply well and probable zones of contamination. The weights are used in a binary integer mathematical programming problem which selects the monitoring locations. On a 100-point rating scale developed to quantify composite plume detection and characterization efficiency, the network design model scored 87, compared with a score of 76 for a pre-existing monitoring network. (The model and pre-existing schemes involve the same number of wells.) The model selects well sites that are close together near the source of contamination, facilitating early detection of a contaminant release, and further apart downgradient, resulting in areal coverage for plume characterization. © 1995.