Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Impact of upstream anthropogenic river regulation on downstream water availability in transboundary river watersheds

This article assesses the adverse impact of upstream anthropogenic regulation of a transboundary river watershed on the natural flow regime of the downstream country, by focusing on a case study: the Diyala (Sīrvān) River watershed shared between Iraq and Iran. The article explores transboundary watershed management difficulties in a three-level system called the transboundary three-scalar framework, which helps to sustainably manage water resources. The average rates of reduction in flow between 2004 and 2013 ranged from nearly 24% in February to about 77% in September. The median of the reduction of rates between June and October was 66.4%

Technical support framework for sustainable management of transboundary water resources

Sustainable management of transboundary rivers, especially in water-scarce regions is increasingly becoming more challenging due to the collective adverse impact of upstream development and climate change on transboundary scale. Two major tributaries of the Tigris River, the Diyala (Sīrvān) and the Lesser Zab River basins, are shared between Iraq and Iran. They were adopted as representative basins for a large number of transboundary rivers, where short-sighted perspectives are currently ruling their management policies. Climate change is anticipated to lead to greater frequency and intensity of droughts, and higher tension is likely to emerge. The authors developed a technical support framework (TSF) that helps decision-making to alleviate the combined negative impact of climate change at basin scale and upstream human-induced impairments. The TSF encompasses six key measures: (1) cross-sectoral trade-offs; (2) improved water-use efficiency and reduction of losses; (3) development of a sound groundwater planning policy; (4) cutbacks in demand while maintaining environmental flow in the river; (5) inter- and intra-basin water transfer systems; and (6) quantification of current supply-demand gaps and sizing a future gaps. The framework supports the sustainable management of water resources in both Diyala and Lesser Zab basins as well as others in common river catchments. The recommendation is that a lower riparian country should put in place measures such as increasing water-use efficiency, rehabilitation of damaged and deteriorated irrigation facilities, and inter- and intra-basin water transfer arrangements to reduce the gap between growing water demands and corresponding supplies

Impact of basin-wide dry climate conditions and non-climatic drivers : an isolation approach

The sustainable management of water resources subjected to the joined influence of transboundary basin-wide dry climatic conditions and intensive man-made river regulations in an upper riparian state on the stream flow regime of a downstream country is a serious challenge. This is particularly the case for arid and semi-arid regions where water resources are limited. The Diyala river basin, shared between Iraq and Iran, was used as an example. The study aims to develop a generic approach to isolate the relative effect of upstream man-made interventions from the mutual impacts of basin-wide dry climate environments and upstream human-induced pressures. The proposed method supports water managers in unbiased, timely and spatially relevant decision-making processes. The streamflow drought index and the monthly-based truncation level were utilized to characterize hydrological droughts, while the standardized precipitation index was used for meteorological drought interpretations. Findings revealed that the upstream river regulation schemes noticeably led to a decline in water availability of the downstream country. The relative impact ranged from a minimum value of 5% in February to the highest value of 54% in July. The average proportional impacts between April and October and between November and March were about 46% and 17%, respectively

Assessment of temporal hydrologic anomalies coupled with drought impact for a transboundary river flow regime : the Diyala watershed case study

Recent increases in human activities in shared river basins have unquestionably raised concerns about potential hydrological impacts, especially impacts of dams and large-scale water withdrawal schemes in the highlands. Anthropogenic pressures twinned with drought impacts have exacerbated water management challenges. This article assesses the cumulative consequences of upstream anthropogenic pressures and drought spells on temporal river flow regimes for the downstream country. The size and complexity of problems confronting transboundary river watersheds makes it necessary to use a representative example basin to study the problems and potential solutions. The Diyala (Sīrvān) river basin, which shares dozens of transboundary watersheds between Iraq and Iran, has been selected as a representative case study. A subset of the Indicators of Hydrologic Alteration (IHA) was utilised and climate variability was considered in assessing the combined effect of various forms of upstream human-river regulations and climatic conditions on natural flow regimes in the downstream state. Findings indicated that the anthropogenic river-regulation coupled with the impact of drought periods have noticeably modified the natural flow paradigm. The yearly average runoffs, which are no longer available for the downstream country, have soared to very high levels, particularly over the last fifteen years. More adverse impacts were detected in the non-rainy season. Findings reveal also that damming and considerable water diversion to large-scale irrigation projects in the upstream state are the main regulations affecting the management of shared water resources in the downstream country

Incorporating the flow duration curve method within the digital filtering algorithms to estimate the base flow contribution to total runoff

The urgent need for rational use of water resources and the intense competition among most of the riparian countries with respect to the use of shared water sources have raised the importance of examining the contribution of base flow to total stream flow. This paper examines the Diyala transboundary river basin shared between Iraq and Iran. Daily unregulated flow records during the hydrologic years between 1955 and 1982 were considered at the upstream flow gauging station and daily unimpaired flow time series during the water years between 1931 and 1961 were examined at the most downstream hydrometric station. Two digital filtering algorithms and the flow duration curve method were applied to extract the base flow time series and compute its signature to total river flow. A generic methodology, which incorporates the flow duration curve method within digital filtering algorithms, has been introduced to obtain the filter parameter α in the filtering algorithms, and obtain the base flow contribution with a high level of confidence. Findings revealed that the base flow proportion is 38 % for the upper sub-basin and 31 % for the upper and middle combined sub-basins. The computed base flow signatures using the incorporated approach have very strong correlation coefficients of around 0.985. The driest year had the highest annual base flow index. The base flow index values started to increase in April and climbed to a peak by the end of May. A gradual decline between August and September was observed. The proposed methodology should be applied to unregulated watersheds

Comparing the export coefficient approach with the soil and water assessment tool to predict phosphorous pollution : the Kan Watershed case study

Water quality protection has become a key concern in water resources development and management. Uncontrolled nutrient input may challenge the quality of some water bodies. This study uses the relatively steep Kan watershed located in the north-west of Tehran (Iran) as an example case study, where an artificial lake is currently under construction for recreational purposes. Two approaches to predict the total annual phosphorous load were assessed: the soil and water assessment tool (SWAT) and the export coefficient approach. River discharge and sediment transport were simulated prior to modeling of the total phosphorous (TP) load in SWAT to make the model more accurate. In addition, an upstream to downstream calibration method was utilized. Findings reveal that the SWAT-simulated phosphorous load had sound Nash–Sutcliffe efficiency (E NS) values (E NS of 75 % for calibration and E NS of 52 % for validation). The relative error in estimating annual TP load was 7 %. The export coefficient approach assigning coefficients of export for each land use is known as an alternative method that can be used for estimating the TP load. Four sets of export coefficients were selected from the literature to examine their suitability in TP load prediction. The results showed significant errors in TP load prediction, which indicates that export coefficients are likely to be watershed-specific. Likewise, the export coefficients were found to vary through four wet months with errors ranging from 9 % to 33 %. This paper demonstrates that the export coefficient method may estimate the pollution load in the Kan watershed with less data than the advance SWAT model. However, it is associated with a higher level of error

Drought indices supporting drought management in transboundary watersheds subject to climate alterations

There is growing concern in Iraq about the inefficiency of reactive drought management practices. Corresponding actions are largely characterized as emergency-based responses that treat the symptoms of drought rather than consider the vulnerability components associated with impacts. The Diyala watershed shared between Iraq and Iran has been used as an example transboundary river basin marked by ineffectiveness of drought management. The standardized precipitation index and the reconnaissance drought index were used to determine the historical meteorological drought episodes and the analysis indicated climate change-induced alterations in the area. Spatiotemporal drought maps were drawn, which can be used for the identification of the drought prone areas and assist proactive planning. The paper discusses the underlying causes of impairments of drought management policies, challenges and difficulties accompanied with the governance of drought in Iraq. Given the influence of climate change and the upstream anthropogenic pressures, the time has come to adopt a gradual nation-wide transition step to drought risk planning incorporating a management approach at transboundary scale. Moreover, the institutional and technical water vulnerability components associated with drought management should be considered in an integrated manner. The paper presents a generic technical template to support decision-makers in drought risk management