Understanding the impact of droughts in the Yarmouk Basin, Jordan: monitoring droughts through meteorological and hydrological drought indices

This article assesses drought status in the Yarmouk Basin (YB), in northern Jordan, using the Standardized Precipitation Index (SPI), the Standardized Water-Level Index (SWI), and the Percent Departure from Normal rainfall (PDNimd) during the years 1993–2014. The results showed that the YB suffers from frequent and irregular periods of drought as variations in drought intensity and frequency have been observed. The SPI results revealed that the highest drought magnitude of − 2.34 appeared at Nuaimeh rainfall station in 1991. This station has also experienced severe drought particularly in years 1995, 1999, 2005, and 2012 with SPI values ranging from − 1.51 to − 1.59. Some other rainfall stations such as Baqura, Ibbin, Khanasiri, Kharja, Mafraq police, Ramtha, Turra, and Umm Qais have also suffered several periods of drought mostly in 1993. The SWI results show the highest extreme drought events in 2001 in Souf well while other extreme drought periods were observed at Wadi Elyabis well in 1994 and at Mafraq well in 1995. As compared to SPI maps, our SWI maps reflect severe and extreme drought events in most years, negatively impacting the groundwater levels in the study area

Glacial lakes of Sikkim Himalaya: their dynamics, trends, and likely fate—a timeseries analysis through cloud-based geocomputing, and machine learning

In the background of ongoing climate change, it is important to monitor the spatial and temporal changes of glacial lakes (GLs) since they influence snowmelt runoff, stream discharge, water resources, and glacial lake outburst flood (GLOF). However, accurate identification and mapping of GLs in the background of snow-clad mountains through visual interpretation of satellite data is a tedious and challenging assignment when multiyear time-series analysis is considered. To overcome this challenge, automated extraction of GLs in satellite images has been carried out in this study with the help of machine learning (ML). The novelty of this study is identification and tracking of GLs over three decades using ML and geospatial analysis using pixel-based image classification. For this, Random Forest Classifier (RFC) and Artificial Neural Network (ANN) were employed. The methodology is demonstrated here for the identification and mapping of GLs in the Sikkim Himalaya from 1987 to 2020 and for forecasting the possible fate of these GLs through time-series modelling. The geospatial time-series analysis using Google Earth Engine, ML classifiers, and GIS framework, has captured the dynamics of GLs in Sikkim and has revealed the spatial and temporal patterns in GLs’ dimensions as well as GLOF risk.</p

Groundwater quality and community health risk in Lalitpur Metropolitan City, Nepal – a geospatial analysis

Groundwater is the main source of drinking water in the Kathmandu Valley (Nepal). To assess the groundwater quality of Lalitpur Metropolitan City (LMC) of this valley, samples were collected in winter and post-monsoon seasons from 35 shallow dug wells and 16 parameters: pH, TDS, EC, Na+, K+, Ca2+, Mg2+, Total hardness, Clˉ, HCO3ˉ, NO3ˉ, NH4+, Fe, PO43-, SO42-, and Total Coliform were analysed. Hydrochemical analysis and GIS-based mapping have revealed spatial and seasonal variations in water quality. The concentration of most of the parameters was higher in the winter samples compared to the post-monsoon. Comparison with the WHO and NDWQS guidelines has revealed anomalous water chemistry. Zones hosting groundwater, suitable and unsuitable for drinking and irrigation were demarcated. However, the presence of pathogens in all the groundwater samples put the entire population of LMC under high health risk. This study bears importance in groundwater exploration, management, and prevention of water-borne diseases

Polytetrafluoroethylene Patch Closure at Venous Anastomotic Site: A Novel Technique for Arteriovenous Graft Salvage

Introduction: The use of prosthetic arterio-venous grafts (avgs) is necessary in patients where all autogenous vein options are exhausted. This study asseses the results of PTFE patch plasty at the venous end of the access anastomosis. Materials and Methods: This is a prospective observational single centre study in a tertiary care centre for all patients with prosthetic AV graft venous anastomotic site stenosis between 2012 and 2015. Results: There were 40 patients in the study period. Presenting symptoms were primarily inadequate dialysis from AV Graft due to thrombosed graft within 14 days duration. The average age was 58.2 years and 70% were male. They underwent thrombectomy and PTFE patch closure at the venous anastomotic site due to AV graft thrombosis in upper extremity. 38.4% patients had both hypertension, Type II DM while 38.4% patients suffered from triad of hypertension, Type II DM and Hyperlipidemia. Criteria of success was based on immediate post operative bruit and next day heparin free hemodialysis from AV Graft. 37 patients who underwent the procedure had primary patency rate of 91.89% at 3 months and 59.45% at 6 months. Mean follow-up time was 8 months with average hospital stay of 3 days without post-operative complications. Conclusion: Treatment of AVG thrombosis should be performed urgently. There is no standard approach for AV graft thrombosis and surgical management must be individualized for each case. As the commonest cause of graft occlusion is at the venous anastomotic site, hence AV graft thrombectomy with eptfe patch closure can achieve better result compared to thrombectomy with primary closure or stent placement

Endovascular Salvage Procedures in Increasing the Longevity of Hemodialysis Access

Introduction: The leading cause of failure for an autogenous or prosthetic arteriovenous hemodialysis access is venous anastomotic stenosis & central venous stenosis. Endovascular procedures have come a long way in treating such lesions without significant postoperative morbidity and reliable technical success rates.This study aims at studying the long term results of such central venous and anastomotic site stenosis treated with endovascular approach in our centre. Materials and Methods: A total of 26 patients were treated, for a duration of 33 months between March 2012 to November 2014 with central venous, anastomotic site angioplasty ± stenting. Patients were followed up for 9 months. We had re-intervention in 3 cases. Results: Inadequate dialysis, thrombosed graft were the commonest presenting symptoms. Primary patency at the end of 15 months was 34.6% (9 patients), & at the end of 20 months was 11.5 %( 3 patients). Conclusion: Endovascular treatment with angioplasty or stenting for central venous stenosis & access salvage is safe, with low rates of technical failure. Only angioplasty without stenting seems by far the preferred approach, since it is less invasive, highly repeatable