Surface Water Flow Balance of a River Basin Using a Shallow Water Approach and GPU Parallel Computing; Pescara River (Italy) as Test Case

The analysis and prevention of hydrogeological risks plays a very important role and, currently, much attention is paid to advanced numerical models that correspond more to physical reality and whose aim is to reproduce complex environmental phenomena even for long times and on large spatial scales. Within this context, the feasibility of performing an effective balance of surface water flow relating to several months was explored, based on accurate hydraulic and mathematical-numerical models applied to a system at the scale of a hydrographic basin. To pursue this target, a 2D Riemann–Godunov shallow-water approach, solved in parallel on a graphical processing unit (GPU), able to drastically reduce calculation time, and implemented into the RiverFlow2D code (2017 version), was selected. Infiltration and evapotranspiration were included but in a simplified way, in order to face the calibration and validation simulations and because, despite the parallel approach, it is very demanding even for the computer time requirement. As a test case the Pescara river basin, located in Abruzzo, Central Italy, covering an area of 813 km2 and well representative of a typical medium-sized basin, was selected. The topography was described by a 10 × 10 m digital terrain model (DTM), covered by about 1,700,000 triangular elements, equipped with 11 rain gauges, distributed over the entire area, with some hydrometers and some fluviometric stations. Calibration, and validation were performed considering the flow data measured at a station located in close proximity to the mouth of the river. The comparison between the numerical and measured data, and also from a statistical point of view, was quite satisfactory. A further important outcome was the capability to highlight any differences between the numerical flow-rate balance carried out on the basis of the contributions of all known sources and the values actually measured. This characteristic of the applied modeling allows better calibration and verification not only of the effectiveness of much more simplified approaches, but also the entire network of measurement stations and could suggest the need for a more in-depth exploration of the territory in question. It would also enable the eventual identification of further hidden supplies of water inventory from underground sources and, accordingly, to enlarge the hydrographic and hydrogeological border of the basin under study. Moreover, the parallel computing platform would also allow the development of effective early warning systems, for example, of floods.

Sustainable Water Flows in Era of Climate Change

The flow of water in rivers is of paramount importance to maintain supply of food and energy requirements to a great extent. The minimum flow in perennial rivers is subjected to groundwater availability, it is further replenished by the water added through precipitation. Climate change not only increases the melting of glaciers and sea level rise, but also influences the surface water flow and quality. As agriculture is directly affected by changing precipitation pattern, the reduction in water resources and untimely addition of water, both act havoc to the food production process. This interconnection makes agriculture even more vulnerable to the scenarios of global warming and climate change. Studies on food-energy-water nexus has opened new avenues of research in sustainable water management. The role of sustainable flow of water in rivers is highlighted which needs to be understood in era of climate change.

Water Temperature and Hydrological Modelling in the Context of Environmental Flows and Future Climate Change: Case Study of the Wilmot River (Canada)

Simulation of surface water flow and temperature under a non-stationary, anthropogenically impacted climate is critical for water resource decision makers, especially in the context of environmental flow determination. Two climate change scenarios were employed to predict streamflow and temperature: RCP 8.5, the most pessimistic with regards to climate change, and RCP 4.5, a more optimistic scenario where greenhouse gas emissions peak in 2040. Two periods, 2018–2050 and 2051–2100, were also evaluated. In Canada, a number of modelling studies have shown that many regions will likely be faced with higher winter flow and lower summer flows. The CEQUEAU hydrological and water temperature model was calibrated and validated for the Wilmot River, Canada, using historic data for flow and temperature. Total annual precipitation in the region was found to remain stable under RCP 4.5 and increase over time under RCP 8.5. Median stream flow was expected to increase over present levels in the low flow months of August and September. However, increased climate variability led to higher numbers of periodic extreme low flow events and little change to the frequency of extreme high flow events. The effective increase in water temperature was four-fold greater in winter with an approximate mean difference of 4 °C, while the change was only 1 °C in summer. Overall implications for native coldwater fishes and water abstraction are not severe, except for the potential for more variability, and hence periodic extreme low flow/high temperature events.

Alectra vogelii (yellow witchweed).

A. vogelii is an annual parasitic weed of legume crops, particularly cowpea and groundnut, in semi-arid areas of East, West, Central and Southern Africa. It is closely associated with cultivation, is occasionally found associated with weeds of fallows but rarely in natural vegetation. Copious seed production and a long-lived seed-bank allow the rapid build up of infestations when susceptible crop cultivars are planted. Tiny seeds are easily spread by wind, surface water flow or in crop seed. The genus Alectra is on the USDA Federal Noxious Weed list. Despite the similar life cycle to Striga species which are listed, and potential for crop damage, A. vogelii does not appear on Noxious weed lists in Australia. An assessment of its global invasive potential is given by Mohamed et al. (2006).

Assessing Water Literacy: Undergraduate Student Conceptions of Groundwater and Surface Water Flow

Given the importance of fresh water, we investigated undergraduate students’ understanding of water flow and its consequences. We probed introductory geology students’ pre-instruction knowledge using a classroom management system at two large research-intensive universities. Open-ended clicker questions, where students click directly on diagrams using their smart device (e.g., cell phone, tablet) to respond, probed students’ predictions about: (1) groundwater movement and (2) velocity and erosion in a river channel. Approximately one-third of students correctly identified groundwater flow as having lateral and vertical components; however, the same number of students identified only vertical components to flow despite the diagram depicting enough topographic gradient for lateral flow. For rivers depicted as having a straight channel, students correctly identified zones of high velocity. However, for curved river channels, students incorrectly identified the inside of the bend as the location of greatest erosion and highest velocity. Systematic errors suggest that students have mental models of water flow that are not consistent with fluid dynamics. The use of students’ open-ended clicks to reveal common errors provided an efficient tool to identify conceptual challenges associated with the complex spatial and temporal processes that govern water movement in the Earth system.

Капиллярно-волновой варп-двигатель

The generation of surface water flow in channels with sources and resonators of capillary oscillations is detected and investigated. Moving devices with a capillary-wave accelerator of the surface fluid flow are demonstrated. The surface flow of liquid in the channel is generated due to the local deformation of the liquid surface by capillary vibrations and the formation of an excess liquid surface on average near the source and the transport of this surface by waves.

Statistical analysis of water quality parameters in the basin of the Nišava River (Serbia) in the period 2009–2018

This paper analyzes water quality from four hydrological stations in the Nišava river basin from 2009–2018 based on the following parameters: pH, conductivity, O2 saturation, BOD5, suspended solids, total oxidized nitrogen, phosphates, turbidity and coliform bacteria. Authors have applied WQI (water quality index) as the most reliable indicator of the watercourses pollution for setting of surface water flow quality. Statistical analysis of variance (ANOVA) using t-test inferential statistical analysis and post-hoc Tukey test were applied to evaluate statistically significant differences between specific data groups. The results show that bad water quality was registered on all the profiles on an annual basis (WQI = 65–71). The river water pH decreases downstream, while values of BOD5, suspended solids, turbidity, TON, phosphates and coliform bacteria gradually increase. The waters of the Nišava at the station Niš belong to the third class of waters and they are mostly loaded with organic matter originating from waste sewage and industrial waters of both urban and rural areas.

Polystructural organization of a landscape: geophysical analysis of geosystems synergy

Эмпирические концепции ландшафтоведения в рамках геофизической парадигмы позволяют ассимилировать физические законы для описания структуры и функционирования геосистем. Исследованы южно-таежные ландшафты конечно-моренной зоны Валдайского оледенения на территории Национального парка «Валдайский». Геоструктуры описываются с помощью параметров силовых геофизических полей – поля силы тяжести и поля инсоляции, которые можно получить на основе морфометрии цифровых моделей рельефа и цифровых данных космической съемки. Выбор небольшого числа главных параметров с ясным физическим смыслом проводится в соответствии с классическими определениями. Обоснование числа и значимости параметров состояния элементарных пикселей и геосистем осуществляется при анализе результатов численного моделирования структуры ландшафтов. Методом дихотомической группировки элементов поверхности рельефа по параметрам состояния (высота, уклон, горизонтальная и вертикальная кривизна, доза прямой солнечной радиации, NDVI) реализован типологический подход к классификации природно-территориальных комплексов (по принципу однородности) и получена структура ландшафтов на уровне урочищ. С другой стороны, функциональный подход позволил построить иерархию водосборных геосистем по морфометрическим параметрам, описывающим перераспределение воды в поле гравитации – уклонам, удельной площади водосбора, горизонтальной и вертикальной кривизне. Все классификации строятся на единой базе данных и могут использоваться для разных прикладных задач. Приводится пример расчета скоростей стока поверхностных вод и на их основе – зонирование водосборных геосистем по времени добегания до контрольных створов. Таким образом, формальный алгоритм выделения наименьших и иерархических единиц поверхности рельефа на основе параметров состояния приобретает фундаментальный геофизический смысл. Понятие полиструктурности ландшафта в этом случае является абсолютно логичным: выбирая те или иные физически содержательные структурообразующие процессы и их параметры, можно реализовать разные классификации ландшафтов, необходимые в прикладных задачах. Empirical concepts of physical geography enable us to apply the physical laws to describe the landscape structure and functioning. The finitely morainic landscapes of the Valdai Glaciation on the National Park “Valdaisky” territory were investigated. A development of geostructures identified by classical landscape analysis can be described by the parameters of power geophysical fields, mainly gravitation and insolation fields. Selection of a small number of main parameters with extremely clear physical meaning is carried out in accordance with the classical definitions of landscape science. Justification of the number and importance of parameters of elementary pixels and geosystems is carried out when analyzing the results of numerical simulation of the structure of landscapes. Using the method of dichotomic grouping of the relief surface elements by the state parameters (height, slope, horizontal and vertical curvature, dose of direct solar radiation, NDVI), the typological approach to the classification of the natural-territorial complexes (according to homogeneity principle) was realized and the structure of landscapes at a level of natural boundaries was obtained. On the other hand, the functional approach allowed to construct the hierarchy of the water-collecting geosystems by morphometic parameters describing the water redistribution in the gravitation field – slopes, drainage factor, horizontal and vertical curvature. All the classifications are constructed on the single base of data and can be used for different applied tasks. An example of calculating the surface water flow rate is presented and, on their basis, a zoning of the water-collecting geosystems, using the flow time to the control sections. If one uses these parameters the formal mathematical algorithm for identification of elementary and hierarchical units of landforms acquires fundamental geophysical interpretation. In this case the concept of landscape patterns multiplicity is quite relevant. By choosing these or other physical parameters and structure-forming processes we have the opportunity to perform various landscape classifications needed in the applied tasks.