Groundwater Responses to Earth Tides: Evaluation of Analytical Solutions Using Numerical Simulation

Harmonic Earth tide components in well water levels have been used to estimate hydraulic and geomechanical subsurface properties. However, the robustness of various methods based on analytical solutions has not been established. First, we review the theory and examine the latest analytical solution used to relate well water levels to Earth tides. Second, we develop and verify a novel numerical model coupling hydraulics and geomechanics to Earth tide strains. Third, we assess subsurface conditions over depth for a range of realistic properties. Fourth, we simulate the well water level response to Earth tide strains within a 2D poroelastic layered aquifer system confined by a 100 m thick aquitard. We find that the non-linear inversion of analytical solutions to match two observations (amplitudes and phases) to multiple unknown parameters is sensible to the initial guess. We reveal that undrained, confined conditions are necessary for the analytical solution to be valid. This occurs for the dominant M$_2$ frequency at depths >50 m and requires specific storage at constant strain of S$_ϵ$ ≥ 10$^{−6}$ m$^{−1}$, hydraulic conductivity of the aquitard of k$_l$ ≤ 5 ⋅ 10$^{−5}$ ms$^{−1}$ and aquifer of k$_a$ ≥ 10$^{−4}$ ms$^{−1}$. We further illustrate that the analytical solution is valid in unconsolidated systems, whereas consolidated systems require additional consideration of the Biot modulus. Overall, a priori knowledge of the subsurface system supports interpretation of the groundwater response. Our results improve understanding of the effect of Earth tides on groundwater systems and its interpretation for subsurface properties

Groundwater Responses to Earth Tides: Evaluation of Analytical Solutions Using Numerical Simulation

Harmonic Earth tide components in well water levels have been used to estimate hydraulic and geomechanical subsurface properties. However, the robustness of various methods based on analytical solutions has not been established. First, we review the theory and examine the latest analytical solution used to relate well water levels to Earth tides. Second, we develop and verify a novel numerical model coupling hydraulics and geomechanics to Earth tide strains. Third, we assess subsurface conditions over depth for a range of realistic properties. Fourth, we simulate the well water level response to Earth tide strains within a 2D poroelastic layered aquifer system confined by a 100 m thick aquitard. We find that the non‐linear inversion of analytical solutions to match two observations (amplitudes and phases) to multiple unknown parameters is sensible to the initial guess. We reveal that undrained, confined conditions are necessary for the analytical solution to be valid. This occurs for the dominant M2 frequency at depths >50 m and requires specific storage at constant strain of Sϵ ≥ 10−6 m−1, hydraulic conductivity of the aquitard of kl ≤ 5 ⋅ 10−5 ms−1 and aquifer of ka ≥ 10−4 ms−1. We further illustrate that the analytical solution is valid in unconsolidated systems, whereas consolidated systems require additional consideration of the Biot modulus. Overall, a priori knowledge of the subsurface system supports interpretation of the groundwater response. Our results improve understanding of the effect of Earth tides on groundwater systems and its interpretation for subsurface properties.Plain Language Summary: Earth tide induced strains in the subsurface lead to well water level fluctuations in groundwater monitoring wells. This groundwater response has been interpreted with analytical solutions to estimate aquifer properties. However, analytical solutions are based on simplified assumptions whose accuracy have not yet been tested. We develop a new approach to simulate the influence of Earth tides on groundwater based on fundamental physical principles. We simulate realistic conditions and compare our results to those from analytical solution to determine the hydraulic and subsurface conditions under which simplified interpretations are valid. Our results improve understanding of the effects of Earth tides on groundwater systems and interpretation of subsurface properties from well water levels.Key Points: We develop and verify a numerical model for the well water level response to Earth tides. Subsurface property estimation requires undrained and confined conditions occurring at depths >50 m. Amplitudes and phases from numerical and analytical solutions systematically diverge reflecting theory simplifications.German Research Councilhttps://doi.org/10.5281/zenodo.695049

Governance arrangements for health systems in low-income countries : an overview of systematic reviews

CITATION: Herrera, C. A., et al. 2017. Governance arrangements for health systems in low-income countries : an overview of systematic reviews. Cochrane Database of Systematic Reviews, 9:1-93, Art. CD011085, doi:10.1002/14651858.CD011085.pub2.The original publication is available at https://www.cochranelibrary.comBackground: Governance arrangements include changes in rules or processes that determine authority and accountability for health policies, organisations, commercial products and health professionals, as well as the involvement of stakeholders in decision‐making. Changes in governance arrangements can affect health and related goals in numerous ways, generally through changes in authority, accountability, openness, participation and coherence. A broad overview of the findings of systematic reviews can help policymakers, their technical support staff and other stakeholders to identify strategies for addressing problems and improving the governance of their health systems. Objectives: To provide an overview of the available evidence from up‐to‐date systematic reviews about the effects of governance arrangements for health systems in low‐income countries. Secondary objectives include identifying needs and priorities for future evaluations and systematic reviews on governance arrangements and informing refinements of the framework for governance arrangements outlined in the overview. Methods: We searched Health Systems Evidence in November 2010 and PDQ Evidence up to 17 December 2016 for systematic reviews. We did not apply any date, language or publication status limitations in the searches. We included well‐conducted systematic reviews of studies that assessed the effects of governance arrangements on patient outcomes (health and health behaviours), the quality or utilisation of healthcare services, resource use (health expenditures, healthcare provider costs, out‐of‐pocket payments, cost‐effectiveness), healthcare provider outcomes (such as sick leave), or social outcomes (such as poverty, employment) and that were published after April 2005. We excluded reviews with limitations that were important enough to compromise the reliability of the findings of the review. Two overview authors independently screened reviews, extracted data and assessed the certainty of evidence using GRADE. We prepared SUPPORT Summaries for eligible reviews, including key messages, 'Summary of findings' tables (using GRADE to assess the certainty of the evidence) and assessments of the relevance of findings to low‐income countries. Main results: We identified 7272 systematic reviews and included 21 of them in this overview (19 primary reviews and 2 supplementary reviews). We focus here on the results of the 19 primary reviews, one of which had important methodological limitations. The other 18 were reliable (with only minor limitations). We grouped the governance arrangements addressed in the reviews into five categories: authority and accountability for health policies (three reviews); authority and accountability for organisations (two reviews); authority and accountability for commercial products (three reviews); authority and accountability for health professionals (seven reviews); and stakeholder involvement (four reviews). Overall, we found desirable effects for the following interventions on at least one outcome, with moderate‐ or high‐certainty evidence and no moderate‐ or high‐certainty evidence of undesirable effects.https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011085.pub2/fullPublisher's versio

Delivery arrangements for health systems in low-income countries : an overview of systematic reviews

CITATION: Ciapponi, A, et al. 2017. Delivery arrangements for health systems in low-income countries : an overview of systematic reviews. Cochrane Database of Systematic Reviews, 9:1-182, Art. CD011083, doi:10.1002/14651858.CD011083.pub2.The original publication is available at https://www.cochranelibrary.comBackground: Delivery arrangements include changes in who receives care and when, who provides care, the working conditions of those who provide care, coordination of care amongst different providers, where care is provided, the use of information and communication technology to deliver care, and quality and safety systems. How services are delivered can have impacts on the effectiveness, efficiency and equity of health systems. This broad overview of the findings of systematic reviews can help policymakers and other stakeholders identify strategies for addressing problems and improve the delivery of services. Objectives: To provide an overview of the available evidence from up‐to‐date systematic reviews about the effects of delivery arrangements for health systems in low‐income countries. Secondary objectives include identifying needs and priorities for future evaluations and systematic reviews on delivery arrangements and informing refinements of the framework for delivery arrangements outlined in the review. Methods: We searched Health Systems Evidence in November 2010 and PDQ‐Evidence up to 17 December 2016 for systematic reviews. We did not apply any date, language or publication status limitations in the searches. We included well‐conducted systematic reviews of studies that assessed the effects of delivery arrangements on patient outcomes (health and health behaviours), the quality or utilisation of healthcare services, resource use, healthcare provider outcomes (such as sick leave), or social outcomes (such as poverty or employment) and that were published after April 2005. We excluded reviews with limitations important enough to compromise the reliability of the findings. Two overview authors independently screened reviews, extracted data, and assessed the certainty of evidence using GRADE. We prepared SUPPORT Summaries for eligible reviews, including key messages, 'Summary of findings' tables (using GRADE to assess the certainty of the evidence), and assessments of the relevance of findings to low‐income countries. Main results: We identified 7272 systematic reviews and included 51 of them in this overview. We judged 6 of the 51 reviews to have important methodological limitations and the other 45 to have only minor limitations. We grouped delivery arrangements into eight categories. Some reviews provided more than one comparison and were in more than one category. Across these categories, the following intervention were effective; that is, they have desirable effects on at least one outcome with moderate‐ or high‐certainty evidence and no moderate‐ or high‐certainty evidence of undesirable effects.https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011083.pub2/fullPublisher's versio

A snapshot of cancer in Chile: analytical frameworks for developing a cancer policy

INTRODUCTION: The South American country Chile now boasts a life expectancy of over 80 years. As a consequence, Chile now faces the increasing social and economic burden of cancer and must implement political policy to deliver equitable cancer care. Hindering the development of a national cancer policy is the lack of comprehensive analysis of cancer infrastructure and economic impact. OBJECTIVES: Evaluate existing cancer policy, the extent of national investigation and the socio-economic impact of cancer to deliver guidelines for the framing of an equitable national cancer policy. METHODS: Burden, research and care-policy systems were assessed by triangulating objective system metrics -epidemiological, economic, etc. - with political and policy analysis. Analysis of the literature and governmental databases was performed. The oncology community was interviewed and surveyed. RESULTS: Chile utilizes 1% of its gross domestic product on cancer care and treatment. We estimate that the economic impact as measured in Disability Adjusted Life Years to be US$ 3.5 billion. Persistent inequalities still occur in cancer distribution and treatment. A high quality cancer research community is expanding, however, insufficient funding is directed towards disproportionally prevalent stomach, lung and gallbladder cancers. CONCLUSIONS: Chile has a rapidly ageing population wherein 40% smoke, 67% are overweight and 18% abuse alcohol, and thus the corresponding burden of cancer will have a negative impact on an affordable health care system. We conclude that the Chilean government must develop a national cancer strategy, which the authors outline herein and believe is essential to permit equitable cancer care for the country