Estimating the thickness of unconsolidated coastal aquifers along the global coastline

Knowledge of aquifer thickness is crucial for setting up numerical groundwater flow models to support groundwater resource management and control. Fresh groundwater reserves in coastal aquifers are particularly under threat of salinization and depletion as a result of climate change, sea-level rise, and excessive groundwater withdrawal under urbanization. To correctly assess the possible impacts of these pressures we need better information about subsurface conditions in coastal zones. Here, we propose a method that combines available global datasets to estimate, along the global coastline, the aquifer thickness in areas formed by unconsolidated sediments. To validate our final estimation results, we collected both borehole and literature data. Additionally, we performed a numerical modelling study to evaluate the effects of varying aquifer thickness and geological complexity on simulated saltwater intrusion. The results show that our aquifer thickness estimates can indeed be used for regional-scale groundwater flow modelling but that for local assessments additional geological information should be included. The final dataset has been made publicly available (https://doi.pangaea.de/10.1594/PANGAEA.880771).</p

Shallow rainwater lenses in deltaic areas with saline seepage

In deltaic areas with saline seepage, freshwater availability is often limited to shallow rainwater lenses lying on top of saline groundwater. Here we describe the characteristics and spatial variability of such lenses in areas with saline seepage and the mechanisms that control their occurrence and size. Our findings are based on different types of field measurements and detailed numerical groundwater models applied in the south-western delta of the Netherlands. By combining the applied techniques we could extrapolate measurements at point scale (groundwater sampling, temperature and electrical soil conductivity (TEC)-probe measurements, electrical cone penetration tests (ECPT)) to field scale (continuous vertical electrical soundings (CVES), electromagnetic survey with EM31), and even to regional scale using helicopter-borne electromagnetic measurements (HEM). The measurements show a gradual mixing zone between infiltrating fresh rainwater and upward flowing saline groundwater. The mixing zone is best characterized by the depth of the centre of the mixing zone &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;mix&lt;/sub&gt;, where the salinity is half that of seepage water, and the bottom of the mixing zone &lt;i&gt;B&lt;/i&gt;&lt;sub&gt;mix&lt;/sub&gt;, with a salinity equal to that of the seepage water (Cl-conc. 10 to 16 g l&lt;sup&gt;−1&lt;/sup&gt;). &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;mix&lt;/sub&gt; is found at very shallow depth in the confining top layer, on average at 1.7 m below ground level (b.g.l.), while &lt;i&gt;B&lt;/i&gt;&lt;sub&gt;mix&lt;/sub&gt; lies about 2.5 m b.g.l. The model results show that the constantly alternating upward and downward flow at low velocities in the confining layer is the main mechanism of mixing between rainwater and saline seepage and determines the position and extent of the mixing zone (&lt;i&gt;D&lt;/i&gt;&lt;sub&gt;mix&lt;/sub&gt; and &lt;i&gt;B&lt;/i&gt;&lt;sub&gt;mix&lt;/sub&gt;). Recharge, seepage flux, and drainage depth are the controlling factors

Sustainability of fresh groundwater resources in fifteen major deltas around the world

Population growth, urbanization and intensification of irrigated agriculture in the world’s deltas boost the demand for fresh water, with extensive groundwater extraction as a result. This, in turn, leads to salt water intrusion and upconing, which poses a threat to freshwater and food security. Managing fresh groundwater resources in deltas requires accurate knowledge about the current status and behaviour of their fresh groundwater resources. However, this knowledge is scarcely present, especially for groundwater at larger depths. Here, we use three-dimensional variable-density groundwater model simulations over the last 125 ka to estimate the volume of fresh groundwater resources for 15 major deltas around the world. We estimate current volumes of onshore fresh groundwater resources for individual deltas to vary between 1010 m3 and 1012 m3. Offshore, the estimated volumes of fresh groundwater are generally smaller, though with a considerably higher variability. In 9 out of 15 simulated deltas, fresh groundwater volumes developed over thousands of years. Based on current groundwater extraction and recharge rates, we estimate the time until in-situ fresh groundwater resources are completely exhausted, partly leading to groundwater level decline and mostly replacement with river water or saline groundwater. This straightforward analysis shows that 4 out of 15 deltas risk complete exhaustion of fresh groundwater resources within 300 m depth in 200 years. These deltas also suffer from saline surface water which means their groundwater resources will progressively salinize. With a fourfold increase in extraction rates, seven deltas risk a complete exhaustion within 200 years. Of these seven deltas, six suffer from saline surface water. We stress that the groundwater of these six vulnerable deltas should be carefully managed, to avoid non-renewable groundwater use. The progressive exhaustion of fresh groundwater resources in these deltas will hamper their ability to withstand periods of water scarcity

The North Sea Benthos Project: planning, management and objectives

The ICES Benthos Ecology Working Group is integrating recent macrobenthic infaunal data (1999-2001) available from various sources, including national monitoring surveys, in North Sea soft bottom sediments. lt is expected to cover most of the North Sea. The main goal is an overall comparison with the North Sea Benthos Survey data of 1986, in order to determine whether there have been any significant changes and, if so, what may be the causal influences (e.g., climate change, fishing impacts). The work will contribute valuable information on several other topics such as habitat classification and the distribution of endangered species. Therefore, in addition to physico-chemical measurements of sediments samples alongside the benthic fauna, information on water depths, temperature, water quality and salinity will be incorporated in the analysis of species and community distributions. Also, we will use existing ecological and hydrographical models for currents, bottom shear stress and carbon input, along with information on the distribution of habitat types, to explain the observed distribution patterns. At the ASC, an overview of the data available will be presented as well as the anticipated outcomes, and the first steps taken to deal with taxonomic differences and other issues affecting the capability to integrate submitted information

The Burden of Trachoma in South Sudan: Assessing the Health Losses from a Condition of Graded Severity

Trachoma is an infectious disease that is endemic to the Republic of South Sudan. In the absence of appropriate treatment recurrent re-infection in an individual will lead to progressively severe states of trachoma, eventually leading to the loss of visual acuity and finally blindness. Here we distinguish between three separate states of disease: trachoma with normal vision, trachoma with low vision and trachoma with blindness. The first of these states, trachoma with normal vision, is the least severe and the impact of this state on a population has not been well investigated. Trachoma, even before any loss of vision, comes with a great deal of pain and social consequences, and thus disability. In this study we employ data from South Sudan and estimate the burden caused by trachoma with normal vision for the first time. In doing so, we also reveal the extent of the gaps in our knowledge surrounding the natural history of trachoma and highlight areas of research that require urgent attention

Short-term health-related quality of life consequences in a lung cancer CT screening trial (NELSON)

Item does not contain fulltextBACKGROUND: In lung cancer CT screening, participants often have an indeterminate screening result at baseline requiring a follow-up CT. In subjects with either an indeterminate or a negative result after screening, we investigated whether health-related quality of life (HRQoL) changed over time and differed between groups in the short term. METHODS: A total of 733 participants in the NELSON trial received four questionnaires: T0, before randomisation; T1, 1 week before the baseline screening; T2, 1 day after the screening; and T3, 2 months after the screening results but before the 3-month follow-up CT. HRQoL was measured as generic HRQoL (the 12-item Short Form, SF-12; the EuroQol questionnaire, EQ-5D), anxiety (the Spielberger State-Trait Anxiety Inventory, STAI-6), and lung-cancer-specific distress (the Impact of Event Scale, IES). For analyses, repeated-measures analysis of variance was used, adjusted for covariates. RESULTS: Response to each questionnaire was 88% or higher. Scores on SF-12, EQ-5D, and STAI-6 showed no clinically relevant changes over time. At T3, IES scores that were clinically relevant increased after an indeterminate result, whereas these scores showed a significant decrease after a negative result. At T3, differences in IES scores between the two baseline result groups were both significant and clinically relevant (P<0.01). CONCLUSION: This longitudinal study among participants of a lung cancer screening programme showed that in the short term recipients of an indeterminate result experienced increased lung-cancer-specific distress, whereas the HRQoL changes after a negative baseline screening result may be interpreted as a relief

Response shift due to diagnosis and primary treatment of localized prostate cancer: a then-test and a vignette study

Aim Whether a prostate cancer diagnosis induces response shift has not been established so far. Therefore, we assessed response shift in men who were diagnosed with localized prostate cancer. Patients and methods Out of 3,892 men who completed a questionnaire before screening, 82 were subsequently diagnosed with prostate cancer. Response shift was assessed in 52 (response 63%) by the then-test (EuroQol self-rating of health, Short-Form 36 mental health and vitality) and a novel method: rating of vignettes relating to side effects of prostate cancer treatment (urinary, bowel and erectile dysfunction). Three then-tests were conducted: two referencing pre-diagnosis (measured pre

Impact of screening for breast cancer in high-risk women on health-related quality of life

The effectiveness of intensive surveillance in women at high risk for breast cancer due to a familial or genetic predisposition is uncertain and is currently being evaluated in a Dutch magnetic resonance imaging (MRI) screening (MRISC) study, in which annual imaging consists of mammography and MRI. Unfavourable side effects on health-related quality of life may arise from this screening process. We examined the short-term effects of screening for breast cancer in high-risk women on generic health-related quality of life and distress. A total of 519 participants in the MRISC study were asked to complete generic health-status questionnaires (SF-36, EQ-5D) as well as additional questionnaires for distress and items relating to breast cancer screening, at three different time points around screening. The study population showed significantly better generic health-related quality of life scores compared to age-/sex-adjusted reference scores from the general population. Neither generic health-related quality of life scores nor distress scores among the study sample (n = 334) showed significant changes over time. The impact of the screening process on generic health status did not differ between risk categories. Relatively more women reported mammography as quite to very painful (30.1%) compared to MRI. Anxiety was experienced by 37% of the women undergoing MRI. We conclude that screening for breast cancer in high-risk women does not have an unfavourable impact on short-term generic health-related quality of life and general distress. In this study, high-risk women who opted for regular breast cancer screening had a better health status than women from the general population