Mapping Groundwater Potential Through an Ensemble of Big Data Methods.

Groundwater resources are crucial to safe drinking supplies in sub-Saharan Africa, and will be increasingly relied upon in a context of climate change. The need to better understand groundwater calls for innovative approaches to make the best out of the existing information. A methodology to map groundwater potential based on an ensemble of machine learning classifiers is presented. A large borehole database (n = 1848) was integrated into a Geographic Information Systems (GIS) environment and used to train, validate and test 12 machine learning algorithms. Each classifier predicts a binary target (positive or negative borehole) based on the minimum flow rate required for communal domestic supplies. Classification is based on a number of explanatory variables, including landforms, lineaments, soil, vegetation, geology and slope, among others. Correlations between the target and explanatory variables were then generalized to develop groundwater potential maps. Most algorithms attained success rates between 80% and 96% in terms of test score, which suggests that the outcomes provide an accurate picture of field conditions. Statistical learners were observed to perform better than most other algorithms, excepting random forests and support vector machines. Furthermore, it is concluded that the ensemble approach provides added value by incorporating a measure of uncertainty to the results. This technique may be used to rapidly map groundwater potential for rural supply or humanitarian emergencies in areas where there is sufficient historical data but where comprehensive field work is unfeasible.

A survey of domestic wells and pit latrines in rural settlements of Mali: Implications of on-site sanitation on the quality of water supplies.

On-site sanitation is generally advocated as a means to eradicate the health hazards associated with open defecation. While this has provided a welcome upgrade to the livelihoods of millions of people in low-income countries, improved sanitation facilities are increasingly becoming a threat to domestic groundwater-based supplies. Within this context, a survey of pit latrines, domestic wells and improved water sources was carried out in a large rural village of southern Mali. All households were surveyed for water, sanitation and hygiene habits. Domestic wells and improved water sources were georeferenced and sampled for water quality (pH, electric conductivity, temperature, turbidity, total dissolved solids, thermotolerant coliforms, chloride and nitrate) and groundwater level, while all latrines were inspected and georeferenced. A GIS database was then used to evaluate the proportion of water points within the influence area of latrines, as well as to underpin multiple regression models to establish the determinants for fecal contamination in drinking supplies. Moreover, an appraisal of domestic water treatment practices was carried out. This revealed that nearly two-thirds of the population uses bleach to purify drinking supplies, but also that domestic-scale treatment as currently implemented by the population is far from effective. It is thus concluded that existing habits could be enhanced as a means to make water supplies safer. Furthermore, population, well and latrine density were all identified as statistically significant predictors for fecal pollution at different spatial scales. These findings are policy-relevant in the context of groundwater-dependent human settlements, since many countries in the developing world currently pursue the objective of eliminating open defecation.

Intensive groundwater use: a silent revolution that cannot be ignored.

Over the last decades, agriculture in arid and semi-arid countries has experienced a true "silent revolution" of intensive groundwater use. Millions of independent farmers worldwide have chosen to become increasingly dependent on the reliability of groundwater resources, and as a result their countries have reaped abundant social and economic benefits. Data from several countries shows that groundwater irrigation presents a much greater efficiency, than surface water irrigation systems, thus contributing to fulfil the motto of "more crops and jobs per drop". If this situation is confirmed globally, the usual world water visions have to be reviewed. However, the "silent revolution" has been carried out with scarce control on the part of governmental water agencies, and thus a series of unwanted effects have developed in certain places. While these by no means justify the pervasive "hydromyths" and obsolete paradigms that voice the frailty of groundwater, appropriate management of groundwater resources remains a worldwide challenge. This paper provides an overview of these issues, and concludes with the necessity there is to educate all levels of society on the importance of groundwater and to create bottom-up user associations to manage aquifers as common pool resources.

[Primary cavity-based lymphoma and HIV infection]. / Linfoma primario de cavidades e infección por VIH.

BACKGROUND: Primary cavity-based lymphomas (PCBL) represent and uncommon group on non-Hodgkin lymphomas associated with AIDS. They present as malignant effusions with no bone marrow or lymph node involvement, although some cases with bone marrow infiltration at advanced stages have been reported. Tumoral cells are monoclonal and are occasionally infected with human herpesvirus type-8 (HHV-8). PATIENTS AND METHODS: The clinical and evolutive characteristics of six HIV-positive patients with PCBL were analysed. In three of them the presence of genetic sequences of HHV-8 in peripheral blood lymphocytes and lymphomatous effusions was investigated by PCR. RESULTS: The mean age of patients was 37 years and 5 were males. The only female patient had been drug abuser, four males were homosexuals and the other promiscuous heterosexual. The mean CD4+ lymphocyte count was 84 x 10(6)/l (range: 20-180) and all of them had been diagnosed of AIDS. The presentation forms were as pericardial effusion in one case, pleural effusion in three and tumoral ascites in two. Two of the male patients had also Kaposi sarcoma (KS). At diagnosis none of them had infiltration of the bone marrow nor lymphadenopathy. Most malignant cells had immunoblastic traits. The effusions had the characteristics of an exudate and the mean value of lactate dehydrogenase (LDH) was 5,255 IU/l (range: 1,500-11,483). In the three cases investigated there was HHV-8 DNA in the lymphocytes present in the lymphomatous effusion and in peripheral blood. The mean survival after diagnosis was 89 days (7-240). The female patient died without therapy seven days after admission and the five male patients were treated with chemotherapy with a poor response. CONCLUSIONS: HIV-related PCBL associated or not with KA appear in severely immunodepressed patients, their behaviour is very aggressive and its clinical course fatal in a short period of time. The are often associated with KS and HHV-8 seems to be the involved causative agent.

[Primary double neoplasias (author's transl)]. / Neoplasias primitivas dobles.

Data of 22 patients with primary double tumors are reviewed, collected from a total of 39.000 clinical protocols of which 1.168 were malignant. All were histologically verified. Criteria were those established by Warren & Gates i.e. a) each tumor must present clear signs of malignancy, b) each tumor must be different from the other, c) all possibility that one tumor may be a metastasis of the other must be excluded. Twelve of the cases were male and 10 female, representing 1.88% of the total with malignancies. In 6 cases both tumors appeared simultaneously, while the time interval was between 1 and 43 years in the remaining 16. Hematologic neoplasias are predominant with 12/44, followed by digestive and urogenital ones with 8/44 in each sub-group. Association between double tumors is assessed and causal factors which may influence or favor the appearance of two or more neoplasias are discussed.

[Extramedullary plasmacytoma. Presentation of 3 cases]. / Plasmocitoma extramedular. Presentación de tres casos.

The authors report three cases of extramedullary plasmacytoma, localized in the oral cavity, deltoid muscle and upper respiratory passages, respectively. The first case was followed for seven years until his death, the second case has been followed during nine years and is still alive and the third one is a recently diagnosed case.