Changes in the hydrological regime and channel morphology as the effects of dams and bridges in the Barakar River, India

2021 ◽  
Vol 80 (5) ◽  
Author(s):  
Sumantra Sarathi Biswas ◽  
Padmini Pani
Keyword(s):  
Hydrological Regime ◽  
Channel Morphology

Effect of small impediments on channel morphology – intermittent rivers in Brazilian drylands.

2021 ◽  
Author(s):  
André Branco ◽  
Jonas Souza
Keyword(s):  
Rural Areas ◽  
River Flow ◽  
Hydrological Regime ◽  
Development Stage ◽  
Channel Morphology ◽  
Small Rivers ◽  
Sediment Retention ◽  
Initial Development ◽  
Longitudinal Connectivity ◽  
Intermittent Rivers

<p>Land use on rural drylands has as its occupation process developing a hydric security and transportations infrastructure system. Dryland tropical systems present fluvial hydrological regime controlled by precipitation inputs, with few or none springs, showing ephemeral and intermittent rivers. Floodway crossings are a widespread infrastructure, on the countryside road network, to cross small creeks, especially intermittent and ephemeral rivers during the rainy seasons. Floodways are concrete or rock block structure, with or without culverts, that allows the river flow goes through or over it. They are part of a set of small longitudinal impediments, like small earth dams and check-dams, and can significantly impact the connectivity, notably by the high density of these impediments on rural areas. This research analysed the effect of floodways crossing on longitudinal connectivity of intermittent small rivers, focusing on morphological and sedimentological impacts in Brazilian Dryland. We analysed four floodways crossing with culverts installed on sandbed intermittent rivers, with upstream catchment are from 10 Km² to 130 Km². The analyses were based on rainfall data, lateral and longitudinal topographic profiles, generate by UAV surveys; and sedimentological samples of upstream and downstream of each structure. The Effective Catchment Area (ECA) was the first step to understand that several dams, and other longitudinal disconnect elements, decrease the ECA sharply, from 2 Km² to 38 Km² of the floodways analysed. Consequently, it affects the magnitude and frequency of water and especially sediment that reaches the floodway crossings. The results reveal the increase of upstream local base level, affecting 500 to 1000 meters, and coarse sediment retention, which is 1.7 to 3.6 times the standard percentage of very coarse sand and gravel. The retained sediment can be re-worked (reconnect) by extreme rainfall/discharges events, recurrence 0,22/year, and when the silting surface reaches the culvert level. The evolution of the upstream silting process is controlled not only by construction age but also by ECA spatiality and changes, and frequency and magnitude of rainfall/discharges events. The results discussion enabled developing an evolution model based on four stages: Installation, Adaptation, Coexistence, and Silting up. The Installation stage is the building process that locally deconfigures the channel morphology and, sometimes, inserts unfamiliar materials on channels. The Adaptation Stage starts with the first flow events that recreate a channel morphology but affected by the floodway, with the beginning of enhanced upstream sedimentation and downstream erosion. The Coexistence stage the disconnectivity effect is evident with the upstream sedimentation moving upstream. The downstream erosion creates a pool, expanding the floodway/riverbed height gap, and progressively increasing the vertical incision downstream. Lastly, when the sedimentation reaches the culvert level or the floodway, sediment retention decreases, and most of the transported sediment overpass the impediment. The frequency and magnitude of flow events control the time to progress through each stage, remembering the ECA analysis importance over space and time. This proposed model that still on initial development stage can help the integrative environmental management on areas impacted by widespread small longitudinal impediments.</p>

ASSESSMENT OF HYDROLOGICAL CHANGES IN THE ŠUŠVĖ RIVER

2015 ◽  
Author(s):  
Gražina ŽIBIENĖ ◽  
Alvydas ŽIBAS ◽  
Goda BLAŽAITYTĖ
Keyword(s):  
Hydrological Regime ◽  
Maximum Flow ◽  
Environmental Flow ◽  
Physical Structure ◽  
River Channels ◽  
Hydrologic Alteration ◽  
Water Conditions ◽  
Flow Components ◽  
The Impact ◽  
Large Floods

The construction of dams in rivers negatively affects ecosystems because dams violate the continuity of rivers, transform the biological and physical structure of the river channels, and the most importantly – alter the hydrological regime. The impact on the hydrology of the river can occur through reducing or increasing flows, altering seasonality of flows, changing the frequency, duration and timing of flow events, etc. In order to determine the extent of the mentioned changes, The Indicators of Hydrologic Alteration (IHA) software was used in this paper. The results showed that after the construction of Angiriai dam, such changes occurred in IHA Parameters group as: the water conditions of April month decreased by 31 %; 1-day, 3-days, 7-days and 30-days maximum flow decreased; the date of minimum flow occurred 21 days later; duration of high and low pulses and the frequency of low pulses decreased, but the frequency of high pulses increased, etc. The analysis of the Environmental Flow Components showed, that the essential differences were recorded in groups of the small and large floods, when, after the establishment of the Šušvė Reservoir, the large floods no longer took place and the probability of frequency of the small floods didn’t exceed 1 time per year.

Forest Management In Mongolia – A Review Of Challenges And Lessons Learned With Special Reference To Degradation And Deforestation

2019 ◽  
Vol 12 (3) ◽  
pp. 133-166 ◽  
Author(s):  
Alexander Gradel ◽  
Gerelbaatar Sukhbaatar ◽  
Daniel Karthe ◽  
Hoduck Kang
Keyword(s):  
Forest Management ◽  
Land Management ◽  
Management Practices ◽  
Forest Health ◽  
Hydrological Regime ◽  
Lessons Learned ◽  
Ecosystem Functions ◽  
Special Focus ◽  
Driven System ◽  
The Status

The natural conditions, climate change and socio-economic challenges related to the transformation from a socialistic society towards a market-driven system make the implementation of sustainable land management practices in Mongolia especially complicated. Forests play an important role in land management. In addition to providing resources and ecosystem functions, Mongolian forests protect against land degradation.We conducted a literature review of the status of forest management in Mongolia and lessons learned, with special consideration to halting deforestation and degradation. We grouped our review into seven challenges relevant to developing regionally adapted forest management systems that both safeguard forest health and consider socio-economic needs. In our review, we found that current forest management in Mongolia is not always sustainable, and that some practices lack scientific grounding. An overwhelming number of sources noticed a decrease in forest area and quality during the last decades, although afforestation initiatives are reported to have increased. We found that they have had, with few exceptions, only limited success. During our review, however, we found a number of case studies that presented or proposed promising approaches to (re-)establishing and managing forests. These studies are further supported by a body of literature that examines how forest administration, and local participation can be modified to better support sustainable forestry. Based on our review, we conclude that it is necessary to integrate capacity development and forest research into holistic initiatives. A special focus should be given to the linkages between vegetation cover and the hydrological regime.

CRITICAL FACTORS OF WATER CONTENT FOR FISH STOCKS IN THE WATER RESERVOIRS OF KAZAKHSTAN

2017 ◽  
pp. 9-18
Author(s):  
Saule Zhangirovna Asylbekova ◽  
Kuanysh Baibulatovich Isbekov ◽  
Evgeniy Vyacheslavovich Kulikov
Keyword(s):  
Water Content ◽  
Water Level ◽  
Water Availability ◽  
Hydrological Regime ◽  
Fishing Effort ◽  
Water Reservoirs ◽  
The Caspian Sea ◽  
Annual Fish ◽  
Commercial Fish ◽  
Fish Stocks

The hydrological regime of water reservoirs in different years has a decisive impact on the abundance of commercial fish stocks and the quality of ichthyocenoses. In this connection in 2015-2016 there was conducted a retrospective analysis and ranking of hydrological regime impact on these factors. The paper gives evaluation of catches and fish stocks under different scenarios of water availability in the main fishing ponds of the Republic of Kazakhstan that give about 80% of the annual fish catch of the country (except the Caspian Sea). There were analyzed 2000 factors of hydrological regime (water level, annual discharge) and 1845 factors of fishing stocks (catches, abundance, fish biomass). The paper determines the critical characteristics of water availability for fish stocks. There have been proposed a number of administrative decisions and actions in case if water content would approach to the critical level. Among them: limitation of fish catches in the following year; widening zones restricted for fishing; intensification of safety measures of the fish young in residual ponds during arid periods; introduction of catch standards for a unit of fishing effort in low-water years, high-water years and years with normal water level in rivers.

HYDROLOGICAL REGIME AND FREEZING OF HUMMOCKY BOGS ON THE EUROPEAN NORTH OF RUSSIA

2019 ◽  
Vol 12 (9-10) ◽  
pp. 38-48
Author(s):  
V. I. Batuev ◽  
I. L. Kalyuzhny
Keyword(s):  
Water Level ◽  
Hydrological Regime ◽  
Average Intensity ◽  
Water Level Rise ◽  
Northern European ◽  
European North ◽  
Bog Waters ◽  
Northern European Russia ◽  
Seasonal Thawing ◽  
First Time

The development of the European North of Russia, where flat and high-hummocky bog complexes are spread, requires information on the processes of formation of their hydrological regime and freezing of this territory. For the first time, based on observational data, for the period from 1993 to 2013, characteristics of the hydrological regime and freezing of hummocky bogs in Northern European Russia are presented, the case study of the Lovozerskoye bog. The observations were carried out in accordance with the unified methods, approved for the specialized network of Roshydromet bog stations. The regularities of the formation of the hydrological regime of hummocky bogs have been revealed: bog water level drops dramatically from the beginning of freezing to the end of March, rises during snow melt period, slightly drops in summer and rises in autumn. The main feature of hummocky bogs is permafrost, which determines their specific structure. It has been discovered that gravitation snowmelt and liquid precipitation waters relatively quickly run down the hummocks over the frozen layer into hollows between them. Levels of bog waters on the hummocks are absent for a longer period of time. In spring, the amplitude of water level rise in swamplands is on average 60–80 cm. Air temperature and insulation properties of snow are the main factors that influence the bog freezing. Hummocks freeze out as deep as 63–65 cm, which corresponds to the depth of their seasonal thawing in the warm period of the year, and adjoin the permafrost. The greatest depth of freezing of the swamplands is 82 – 87 cm, with an average of 68 cm. The frozen layer at swamplands thaws out from both its upper and bottom sides. The melting of the frozen layer at hummocks occurs only from the bog surface with an average intensity of 0,51 cm/day.

Natural regeneration of pine after ground fires on the territory of the Leningrad region

2016 ◽  
Author(s):  
Д.В. Гусев
Keyword(s):  
Natural Regeneration ◽  
Woody Plants ◽  
Hydrological Regime ◽  
Forest Litter ◽  
Southern Taiga ◽  
Leningrad Region ◽  
Good Recovery ◽  
Burned Areas ◽  
Pine Regeneration ◽  
Positive Effect

Естественное возобновление является важным фактором формирования насаждений, особенно главных лесообразующих пород. Растительное сообщество становится жизнестойким при условии способности восстановить численность популяций заменой погибших экземпляров новыми. Было выяснено в каком количестве происходит естественное возобновление сосны на гарях по сравнению с граничащими участками, не пройденными пожарами, взятые в качестве контроля. Район исследований относится к южной подзоне тайги на территории Ленинградской области в Кировском и Лужском лесничествах. Объектом исследований стали сосновые насаждения, где работы проводились в летний период с 2013 по 2015 год. Всего подобрано 36 участков (включая контроль) размером не более 0,3 га. Учет подроста проводился на учетных площадках. Каждая учетная площадка закладывалась при помощи шеста длиной 178,5 см. Площадь круговых площадок составляла 10 м2, они расположены последовательно друг за другом с непосредственным примыканием. На каждой площадке проводили перечет подроста и делили его по высоте на три категории крупности: мелкий до 0,5 м, средний – 0,6–1,5 м и крупный – более 1,5 м. А также естественное возобновление на участках делили по густоте – на три категории: редкий – до 2 тыс., средней густоты – 2–8 тыс., густой – более 8 тыс. растений на 1 га; по распределению по площади – на три категории в зависимости от встречаемости. Анализ послепожарного возобновления в сосняках показал, что на пробных площадях наблюдается отличное возобновление подроста сосны и обилие на площади, все это связано с уничтожением лесной подстилки, увеличением минерализации почвы что, в конечном счете, положительно влияет на естественное лесовосстановление, о чем свидетельствует появление всходов, а также лучше становится гидрологический режим почвы. Благодаря этому происходит хорошее восстановление. Количество благонадежного подроста составляет от 3,5 до 11,9 тыс. шт./га и его достаточно для естественного восстановления ценопопуляции после пожара. Подтверждена зависимость количество самосева и толщины лесной подстилки. Прогретая после пожара, богатая минеральными веществами почва благоприятна для появления всходов и самосева древесных растений. Natural regeneration is an important factor in the formation of plantations, especially the main forest-forming species. Plant community becomes viable, provided the ability to recover populations, replacement of lost copies new. Find out how much happens in a natural pine regeneration in burned areas compared to adjacent areas not affected by fires, are taken as a control. The study area belongs to the subzone of southern taiga on the territory of Leningrad region, the Kirov and Luga districts. The object of research became pine plantations where the work was carried out in year period from 2013 to 2015. Just picked up 36 stations (including the control) no larger than 0.3 hectares. accounting for the undergrowth was conducted on index sites. Each user platform was laid with a pole length of 178.5 cm the area of the circular pads was 10 m2, they are located successively one after another with a direct connection. At each site conducted the translation of the undergrowth and it was divided in height into three categories of size: small up to 0.5 m, average 0.6 to 1.5 meters and large – more than 1.5 meters. And natural regeneration on plots divided by the density for three categories: rare – up to 2 thousand, medium density – 2 to 8 thousand, thick – more than 8 thousand plants per 1 ha; on the distribution of the area – into three categories depending on the occurrence. Analysis of post-fire regeneration in pine forests showed that the sample areas there is a great renewal of undergrowth of pine and the abundance on the square, all this is due to the destruction of forest litter, increasing salinity of the soil which, ultimately, has a positive effect on natural regeneration, as evidenced by the appearance of seedlings, as well as better hydrological regime of the soil. Which a good recovery. The number of reliable undergrowth is from 3.5 to 11.9 thousand PCs/ha, enough for natural regeneration of seedlings after the fire. Confirmed the dependence of the number of self-seeding and thickness of forest litter. After the fire-warmed, mineral-rich soil is favorable for emergence and self-seeding of woody plants.

Sign in / Sign up

Export Citation Format

Share Document