Perennial Flow Research Articles

Variability of methane content and fluxes in the rybinsk reservoir based on field observations in different seasons of the year

The formation of methane fluxes in the Rybinsk reservoir and the variability of its content in water were investigated during several field campaigns on the reservoir in different seasons. The Rybinsk reservoir is a very large, relatively shallow, low-flow, mesotrophic-eutrophic, morphologically complex basin-valley type reservoir with perennial flow regulation, created on the Upper Volga in 1941. In total, water and air sampling was carried out at 71 stations to determine methane concentration, which was combined with measurements of water column characteristics . As a result, a network of reference stations was established, where regular measurements are made, as well as additional stations in the water area and river estuaries. For control purposes, water samples were taken at the hydroelectric power plant units and downstream of the Sheksninskaya HPP dam, placed within the Rybinsk city. In general, the Rybinsk reservoir is characterised by relatively low methane concentrations - at most stations the average content of dissolved CH4 in water does not exceed 20 µl/l. The lowest concentrations were observed during the winter period. Methane fluxes from the surface of the Rybinsk reservoir vary from 4 to 718 mgC-CH4 m-2 day-1. Specific fluxes in summer period are larger than those measured in autumn, also in summer the spatial variability of the measured fluxes is more significant. Flux values depend on reservoir stratification, oxygen content in water, organic matter in bottom sediments and other factors. Methane degassing through the dam is significantly less than the fluxes from the surface.

Benthic macroinvertebrate dynamics and responses to environmental factors in spring habitats of Kashmir Himalaya

ABSTRACT Understanding the dynamics of the macroinvertebrate community and the environmental influences is crucial for effective management and conservation of springs. This study examines diversity and spatio-temporal variation in macroinvertebrate assemblages across 12 spring habitats in the South Kashmir Himalayas. Macroinvertebrates were collected, sorted, identified, and enumerated from spring habitats on a seasonal basis from 2013 to 2015, and subjected to various statistical tests. Through statistical tests, significant distinctions are observed among springs and seasons. Permutational analysis of variance showed significant differences in macroinvertebrate assemblages across springs and seasons using both abundance and presence–absence data. Alpha diversity metrics depict variations in richness and Shannon’s H across springs. β-diversity evaluation reveals significant differences in macroinvertebrate assemblages across springs based on abundance and presence–absence data. So, the spring sites present homogeneity in group dispersion (composition varies similarly) while having significantly different compositions. Physicochemical factors like temperature, dissolved oxygen, sulphate, nitrate-nitrogen, and substrate heterogeneity strongly influence the assemblage. In addition, substrate heterogeneity, perennial flow, and spring size also played an important role in explaining the assemblage patterns. The present study provides important information on the impact of environmental factors on the ecological characteristics of macroinvertebrate assemblages vital for effective conservation and monitoring.

Challenging the Atacama desert: Agronomic and water conditions for pre-Hispanic maize agriculture in hyper arid environments inferred by δ18O isotopes

During the Formative Period (ca.2400–950 years BP), pre-Hispanic farmers in Pampa del Tamarugal developed a complex agricultural system in the hyper-arid Atacama Desert in Tarapacá, northern Chile. This system involved numerous agricultural fields congregated near the Tarapacá Valley’s perennial stream and the Guatacondo ravine’s ephemeral stream. Well-established villages such as Caserones, Pircas, Ramaditas, and Guatacondo accompanied these developments. However, the importance of understanding the water sources has been neglected despite the efforts to understand the relationships between pre-Hispanic agriculture and their living environment. Thus, we presumed the use of local water sources without a clear understanding of their exploitation methods or the associated technological implications. Furthermore, there is limited research on groundwater use in Tarapacá. This research aims to understand water sources used in the cultivation of maize (Zea mays) using δ18O isotope values obtained from pre-Hispanic maize kernels in Tarapacá. We compared these values with published δ18O values of water sources and applied a generalized linear model (GLM) with a Gaussian distribution, performing a Tukey’s post hoc test for multiple comparisons of means with heteroscedasticity-consistent covariance estimation. The best-fit model was identified using a stepwise model selection procedure based on the Bayesian information criterion (BIC). Our results indicate that mean δ18O values of organic matter from maize kernels range from 24.73 ‰ to 31.65 ‰. The best performing model on δ18O only included Group (BIC=298.2) as the explanatory variable as Period, Site, and Weight had no effects. These findings point towards a significant statistical relationship between the δ18O values of organic matter derived from maize kernels and the specific geographic regions they originate from. These values also show an enrichment of δ18O isotope in Tarapacá samples, except for Pica 8. These results indicate diverse agricultural strategies that utilized different water sources including perennial flow in the Tarapacá River, ephemeral runoff at Guatacondo, and groundwater in the Pampa del Tamarugal. Also, due to the enrichment of δ18O, we suggest that the circular structures found among the fields were used as water reservoirs leading to the observed enrichment of δ18O isotope values. We discuss the role of ancient agriculture technology in water management, the role of maize, cultural strategies, and the relationships with their environment. In conclusion, pre-Hispanic farmers managed limited water sources successfully despite intermittent drought for hundreds of years until the 1970 s, when agriculture was abandoned due to multiple factors.

Evaluating the comprehensive flood impact assessment on the head reach of the Chiniot dam project

The major sources of surface water available to Pakistan are perennial flows of the River Indus and its tributaries i.e. Jhelum and Chenab Rivers. The creation of a reservoir of 0.9 MAF Capacity will cause the water level to rise and reduction in flow velocity on the Chenab River upstream of Chiniot Bridge. Consequently, it will cause sediment deposition which would further increase the water level due to the raised river bed level by deposited sediments. To study this storage, the reservoir has been modelled in HEC-RAS software to assess pre-dam and post-dam scenarios to simulate different conditions of river flow for water surface profile and sediment delta modelling of the reservoir reach, using historical daily water and sediment flows (1985–2022). The results of flood routing showed that the reservoir has attenuated the peak flood volume with safe releases at downstream side with proper operation of spillway gates. The average sediment inflow in the reservoir is worked out to be 38.4 metric tons. The results of sediment modelling and reservoir flood management indicated that after every 05 years of normal reservoir operation, reservoir flushing is recommended. Without sediment flushing, the river bed would be further raised beyond 189.0 m due to incoming sediment, resulting in further rise of water level up to 192.8 m which is the existing crest level of upstream training works of Talibwala Motorway Bridge.

Conservation and characterization of karst water using morpho-hydrogeological methods in Pindul Cave system, Gunungsewu Karst, Java, Indonesia

Pindul Cave system is one of the essential water resources in Wonosari Basin. Pindul Cave has a perennial flow and is used to cave tubing. Administratively, this research was conducted in Pindul Cave and its surrounding areas located in Karangmojo District, Gunungkidul Regency. The aim of this research are: (1) to analyze the underground flow system in Pindul Cave (2) to estimate the catchment area of Pindul Cave using morphology approach (3) to propose management action of the catchment area. The method used in this study using a survey method that is divided into several stages include the preparation stage, the fieldwork stage, and the post-field stage. The preparation stage includes site selection study, discharge measurement site selection, site selection, and injection of dye tracer. The fieldwork stage is ground check survey, discharge measurements, and tracer tests. The post-field stage is analyze breakthrough curve, and making the management action of catchment area. The results of this research are: (1) based on tracer test result show that, Pindul cave stream is supplied from 2 sources, namely those originating from the cave system and those originating from surface runoff; (2) the estimated catchment area of the Pindul Cave system using a morphological approach is 15,44 km2; (3) Propose management action for the catchment area of the Pindul Cave system are not mining in the upstream area, not throwing garbage in the upstream underground river, continuing to apply the rules with restrictions on visitors to Pindul Cave in accordance with the carrying capacity.

Intermittent rivers and ephemeral streams are pivotal corridors for aquatic and terrestrial animals

Abstract Rivers are efficient corridors for aquatic animals, primarily under the assumption of perennial flow. However, the recognition that river drying is a common and widespread phenomenon requires reexamining animal movement through river networks. Intermittent rivers and ephemeral streams have been overlooked when studying animal movement, even though approximately 60% of the global river network dries. In the present article, we extend the current focus of river ecology by integrating the effects of drying on the movement of aquatic and terrestrial animals. Moreover, we introduce a conceptual model that challenges the current bias, which is focused on perennial waterways, by encompassing animal movement across hydrologic phases (nonflowing, flowing, dry, rewetting) and habitats (aquatic, terrestrial). We discuss their corridor function in conservation and restoration planning and identify emerging research questions. We contend that a more comprehensive and inclusive view of animal movement in dry channels will advance ecological understanding of river networks and respective conservation efforts.

Loss of functionally important and regionally endemic species from streams forced into intermittency by global warming.

Climate change is altering hydrological cycles globally, and in Mediterranean (med-) climate regions it is causing the drying of river flow regimes, including the loss of perennial flows. Water regime exerts a strong influence over stream assemblages, which have developed over geological timeframes with the extant flow regime. Consequently, sudden drying in formerly perennial streams is expected to have large, negative impacts on stream fauna. We compared contemporary (2016/17) macroinvertebrate assemblages of formerly perennial streams that became intermittently flowing (since the early 2000s) to assemblages recorded in the same streams by a study conducted pre-drying (1981/82) in the med-climate region of southwestern Australia (the Wungong Brook catchment, SWA), using a multiple before-after, control-impact design. Assemblage composition in the stream reaches that remained perennial changed very little between the studies. In contrast, recent intermittency had a profound effect on species composition in streams impacted by drying, including the extirpation of nearly all Gondwanan relictual insect species. New species arriving at intermittent streams tended to be widespread, resilient species including desert-adapted taxa. Intermittent streams also had distinct species assemblages, due in part to differences in their hydroperiods, allowing the establishment of distinct winter and summer assemblages in streams with longer-lived pools. The remaining perennial stream is the only refuge for ancient Gondwanan relict species and the only place in the Wungong Brook catchment where many of these species still persist. The fauna of SWA upland streams is becoming homogenised with that of the wider Western Australian landscape, as drought-tolerant, widespread species replace local endemics. Flow regime drying caused large, in situ alterations to stream assemblage composition and demonstrates the threat posed to relictual stream faunas in regions where climates are drying.

Comparing morphological, parasitological, and genetic traits of an invasive minnow between intermittent and perennial stream reaches

Abstract Invasive fishes are a major environmental issue at the global scale, particularly for their impacts on freshwater ecosystems via the mechanisms of hybridisation, competition, predation, and disease transmission. This is of special conservation concern on the Iberian Peninsula due to the high level of endemism. With the aim to improve our knowledge on the invasion process of non‐native fishes, the present study consists of analysing key biological traits potentially related to their colonisation capacity: morphology, parasite communities, and genetic diversity. A non‐native population of Languedoc minnow Phoxinus septimaniae (leuciscid species native to south‐east France) was assessed in Tordera Stream (north‐eastern Iberian Peninsula). Fish were sampled in mid‐May (reproductive period) 2018 and 2019. Biological traits were compared between colonising and resident individuals from stream reaches of intermittent and perennial flow, respectively. After adjusting for fish size/body mass with analysis of covariance, body condition and health status (external and internal examination) tended to be better in the intermittent reach. Parasite load (number) and diversity (Shannon index) were significantly higher in the perennial reach. Fish development was also more stable in colonising minnow, as detected by low levels of fluctuating asymmetry for the eye diameter and the length of pectoral fins (adjusted for bilateral character size). Genetic diversity (microsatellite markers) was lower in resident minnow. Minnow genetic homozygosity (index of internal relatedness) was positively associated with parasite load and developmental instability (high fluctuating asymmetry levels). Our results show that colonising minnows display particular profiles of morphological, parasitological, and genetic traits that apparently allow these individuals to increase their dispersal capacity to survive and reproduce in harsher environmental conditions. The potential mechanisms may be related to a wider physiological tolerance, better immune response, parasite resistance/tolerance, and genetic diversity in colonising specimens. Such information reveals the specific traits of successful fish invaders under a seasonal colonisation dynamic. These data are relevant for environmental managers, to predict and identify areas vulnerable to invasion, in order to establish monitoring programmes for early detection, which will help to reduce the spread of non‐native fish populations.

Estimation of groundwater potential zones using remote sensing and geographical information system technique- Waghai Taluka, Dang district, Gujarat, Western India

Groundwater is an important natural resource and has a significant role in the economy of any nation. The Dang district situated in the south-eastern part of the Gujarat state, Western India faces potable water problems in almost every summer season though the region receives heavy rainfall during monsoon months. The region has steep slopes causing heavy runoff during monsoon. The people of the district mainly rely on agriculture and the major source of the surface water is the perennial flows in Ambika, Purna and Khapri rivers that criss-crosses the district. In this study, we have employed an integrated approach to find out the groundwater potential regions in the Waghai Taluka based on geology, geomorphology, tectonic set-up, present wells’ static ground water level and slope length of the region. The field observations were also considered for the verification of our final inputs. The thematic maps are prepared with the use of remote sensing and GIS tools. The groundwater potential zones are classified into potential and non-potential zones based on integrated results and verified with existing well sites in study region. It was found that about 11% of the area comes under non-potential zones has least prospect of finding groundwater, while 89% of the region has more probability of finding groundwater under the potential zones.

Effects of flow recession regime on stranding of Rio Grande silvery minnow suggests that conservation actions must overcome evolutionary traps

Abstract Flow intermittence is a major disturbance for riverine fishes. Many species of fishes that evolved in naturally intermittent streams have specialized adaptations to survive drought such as movement to refuge habitats. Conservation of fishes in river systems with highly altered flow regimes requires understanding of how individuals and populations respond to flow intermittence. Here, flow was manipulated in two 16‐km segments of the Rio Grande, New Mexico, to determine whether managed flow recession could reduce stranding imperilled Rio Grande silvery minnow in isolated pools. Slower flow recessions did not decrease stranding in isolated pools over the range tested. Flow recession rate appeared to have an adverse impact on stranding; fewer fish were stranded under faster recession rates, but complex interactions were evident. Fish were stranded throughout both segments regardless of flow recession rate. No evidence of a synchronized movement response was observed. Instead, many Rio Grande silvery minnows were probably trapped within proximal habitats, which dry completely and function as evolutionary traps, rather than moving to areas of perennial flow. Use of proximal habitats during streamflow intermittence has implications for management of the species and mitigation of mortality, including managed flow recession rates, and position and function of refuge habitats. Effective mitigation for flow intermittence and stranding in streams with highly modified flow regimes will depend on the life history and behavioural response of the species. For Rio Grande silvery minnow, facilitating adaptive behaviour would require creating refuge areas that increase fish survival for weeks to months, as reducing the attractiveness of the traps is likely to be impossible given lack of a synchronized movement response to declining flows. Mismatching life‐history strategies, behaviour, and scale of conservation actions may result in ineffective management and continued dependence on intensive management actions such as augmentation with hatchery fish.

Identifying and estimating the sources of river flow in the cold arid desert environment of Upper Indus River Basin (UIRB), western Himalayas

A reliable water supply in different Himalayan River basins is increasingly important for domestic, agriculture, and hydropower generation. These water resources are under serious threat due to climate change, with the potential to alter the economic stability of 237 million people living in the Indus River Basin alone. In the present study, we used new stable water isotope data set to identify and estimate the different sources of streamflow and their controlling factors in the Upper Indus River Basin (UIRB), India. The data set presented wide spatial and temporal variability without the distinct isotopic signature of various sources of river flow. However, variable but distinct signatures of sources of river/stream flow exist at the sub-basin or catchment scale. These variabilities are ascribed to changing physiographical, meteorological, and local climatic conditions. Further, the distinct microclimatic conditions including altitudinal variability, aspect slope, etc. govern the spatio-temporal variability of sources and streamflow, hence different lapse rates at sub-basin/catchment scale. The study suggested that the contribution of snowmelt and glacier melt to river flow varies spatially and temporally. The Bayesian mixing model results suggested that snowmelt contribution is higher in Indus (63 ± 1.2%) and Shyok (58 ± 1.7%) while as, glacier melt contribution is higher in Nubra 64 ± 2.3% and Suru 60 ± 2.7% sub-basins/catchments. The groundwater contribution (baseflow) sustains and regulates the flow in rivers/streams during winter and spring, which is very vital for the local water supply. The study suggests that the spatially diverse rugged topography and microclimate in UIRB dominantly control the differential contribution from various sources of river flow. The warming climate, which has resulted in a decrease in solid precipitation, continuous glacier mass loss, early melting of snow cover, etc., would have an inconsistent impact on the perennial flow of rivers with the potential to alter the economic and political stability in the region.

Long-lasting effects of experimental flow intermittency on alpine stream macroinvertebrates (Val Roseg, Switzerland)

Changing weather patterns and receding glaciers are predicted to increase flow intermittency in alpine streams. If aquatic macroinvertebrate communities largely comprise taxa adapted to perennial flows, an increase in flow intermittency substantially reduces biodiversity and affects functional processes. We conducted a before-after-control-impact field experiment to examine how macroinvertebrate communities in an alpine headwater stream responded to and recovered from a repeated experimental increase in flow intermittency. Flow in one channel was manipulated to simulate increased summer intermittency (June–September) over two consecutive years, whilst an adjacent channel served as a control. We monitored the density of benthic macroinvertebrates, periphyton and organic matter at approximately monthly intervals over three years during the snow-free period. Before manipulation, both channels had similar ecological properties. The flow manipulation reduced the overall macroinvertebrate density, and especially the proportional rheophile density, across both years. Recovery of the macroinvertebrate community following experimental flow intermittency took more than a year, and longer than our study period. This could be due to long aquatic life stages, dispersal limitation and biotic interactions. We conclude that climate-induced changes in alpine stream flow regimes can lead to a fundamental shift in macroinvertebrate assemblages through local extinctions, mostly of rheophilic species.

Linear Modeling-Based Assessment Of Water Quality Of River Yamuna, India (2011-2020)

Since time immemorial, rivers have been the lifelines of billions worldwide. They provide fresh water for drinking, agriculture, bathing, and fulfill our various requirements. There is no life without water; hence, making sure that perennial flows remain unpolluted is one of man’s prime duties. On the contrary, many industrial chemicals that pollute our water resources are common in the present times. The entire stretch of Yamuna River, from Yamunotri glacier to its confluence with the river Ganges at Allahabad, is used for various human activities. The various pollution sources, such as residential, industrial, and agricultural areas, induce many substances in the river. Domestic sources cause about 85% of the total pollution. Large clusters of industries established at Kota, Gwalior, Indore, Nagda, Khetri, Yamuna Nagar, Panipat, Sonepat, Delhi, Baghpat, Ghaziabad, Gautam Budha Nagar, Faridabad, Mathura release vast amounts of pollutants in River Yamuna. The nutrients and pesticides from agricultural fields are adsorbed by the sediment particles and reach the river, particularly during early floods. These chemicals geo-accumulate in riverbeds. The dumping of worshiping material and ashes in the water further degrades the water quality. High organic content, increased nutrients, pathogens, pollutants, and deforestation in the catchment and river usage as transport media adversely affect the river water quality. Many activities such as bathing, washing clothes, religious activities, offering of flowers, garlands, and other worship materials are also responsible for river pollution in India. This paper studies the effect of pollution on the River Yamuna and concentrates on studying water quality parameters of the entire stretch of River Yamuna flowing through five geopolitical states of India. The second part deals with the study of pollution-induced by various drains emptying their flow into River Yamuna. It also includes a study during the extraordinary condition induced by COVID-19 lockdown.

Water quality in three potential drought refuges in an arid-land river: assessing habitat suitability for at-risk fish species

Drought is a common disturbance in arid-land streams and rivers. The survival of aquatic species depends on access to refuge habitats where water quality remains high. Over the past century, modified flow regimes and altered watershed and instream characteristics have led to the extinction and endangerment of numerous fish species endemic to the southwestern United States. We assessed the water quality of potential drought refuges in the Middle Rio Grande (MRG), with an emphasis on suitability for the endangered Rio Grande Silvery Minnow (RGSM). We examined three types of potential drought refuges: three agricultural return drain outfalls; three isolated pools that remained during streamflow intermittency; and a reach with perennial flow below an agricultural diversion dam. All potential refuges are known to contain RGSM and other fishes. Two out of three drain outfalls, one out of three isolated pools, and three out of ten kilometers of perennially wetted stream below a dam met basic water quality criteria necessary to support RGSM populations. These findings suggest that refuge habitability is context dependent, that generalizations regarding the suitability of a specific refuge type should be avoided, and that careful assessment is required to determine if a specific location will support fish assemblages. Although some areas may contain water, they may represent ecological traps if fish are exposed to poor water quality conditions compared to other potential refuge habitats.

Groundwater-surface water interactions and flux of organic matter and nutrients in an urban, Mediterranean stream

The chemical quality of dissolved organic matter (DOM) and the speciation of nitrogen exported from urban catchments is of great importance to biogeochemical cycling in riverine and coastal receiving waters. Many urban streams in Mediterranean climates have a flashy hydrologic regime, which would suggest a rapid pulsing and shunting of solutes downstream. However, the role of these systems both as passive pipes for solute transport or as reactors for DOM and nutrient transformation is still an open question for urban, Mediterranean streams. To address this question, we evaluated changes in concentrations of inorganic and organic solutes and DOM optical properties in Alvarado Creek, a perennially-flowing, urban, first-order tributary of the San Diego River in San Diego, CA, USA, during dry weather (baseflow) conditions and during four storm events in 2016–2018. Chloride and sulfate concentrations corroborate the supposed saline groundwater supply that maintains perennial flow and brackish nature in this urban stream. During dry weather, high proportions of protein-like fluorescent component (AC4) and downstream decreases in total dissolved nitrogen (TDN) and nitrate imply in-stream processing (nitrification and denitrification). By contrast, storm hysteresis curves indicate that the supply of DOM and TDN was not exhausted over the duration of a storm event, whereas nitrate was eventually depleted, presumably because nitrification could not keep up with the export of nitrate from source areas. Rapid decreases in chloride during the storm hydrograph coincided with a shift in specific ultraviolet absorbance (SUVA) and fluorescence index (FI) to more terrestrially-derived and aromatic carbon sources, most likely from interflow of stormwater through vadose zone soils. On an annual basis, the export of microbially-derived DOM during dry weather was higher than the export of terrestrially-derived DOM during storm events; both represent important carbon inputs to coastal waters.

Hydrological responses to rainfall events including the extratropical cyclone Gloria in two contrasting Mediterranean headwaters in Spain; the perennial font del Regàs and the intermittent Fuirosos

AbstractCatchment hydrological responses to precipitation inputs, particularly during exceptionally large storms, are complex and variable, and our understanding of the associated runoff generation processes during those events is limited. Hydrological monitoring of climatically and hydrologically distinct catchments can help to improve this understanding by shedding light on the interplay between antecedent soil moisture conditions, hydrological connectivity, and rainfall event characteristics. This knowledge is urgently needed considering that both the frequency and magnitude of extreme precipitation events are increasing worldwide as a consequence of climate change. In autumn 2018, we installed water level sensors to monitor stream water and near‐stream groundwater levels at two Mediterranean forest headwater catchments with contrasting hydrological regimes: Font del Regàs (sub‐humid climate, perennial flow regime) and Fuirosos (semi‐arid climate, intermittent flow regime). Both catchments are located in northeastern Spain, where the extratropical cyclone Gloria hit in January 2020 and left in ca. 65 h outstanding accumulated rainfalls of 424 mm in Font del Regàs and 230 mm in Fuirosos. During rainfall events of low mean intensity, hydrological responses to precipitation inputs at the semi‐arid Fuirosos were more delayed and more variable than at the sub‐humid Font del Regàs. We explain these divergences by differences in antecedent soil moisture conditions and associated differences in catchment hydrological connectivity between the two catchments, which in this case are likely driven by differences in local climate rather than by differences in local topography. In contrast, during events of moderate and high mean rainfall intensities, including the storm Gloria, precipitation inputs and hydrological responses correlated similarly in the two catchments. We explain this convergence by rapid development of hydrological connectivity independently of antecedent soil moisture conditions. The data set presented here is unique and contributes to our mechanistic understanding on how streams respond to rainfall events and exceptionally large storms in catchments with contrasting flow regimes.

Geological permeability controls streamflow generation in a remote, ungauged, semi-arid drainage system

Study regionA semi-arid drainage system overlying a thick (12 km) sedimentary sequence on the Dampier Peninsula in northwestern Australia. Study focusIn this study we combine aerial geophysics, geological mapping, hydrometry and hydrochemistry with aerial image analysis and stream mass balance modeling to delineate the key hydrogeological structures and processes that control streamflow generation within a remote ungauged semi-arid watershed. New hydrological insights for the regionFour distinct processes of streamflow generation were identified, each dependent on the spatial distribution of lithological permeability; (1) ephemeral rainfall runoff over low-permeability surface lithologies, (2) intermittent flow generated by seasonal groundwater discharge from the unconfined aquifer above a newly mapped clay layer, (3) persistent flow from contact springs via interbedded high- and low-permeability layers, and (4) perennial flow associated with regional groundwater discharge at headwater springs. This study highlights the importance of geological permeability and the resultant hydrogeological processes as controls on streamflow generation, particularly in low-relief and arid regions where topography is less likely to determine the distribution of streamflow.

Precambrian fans on opposite margins of an intracratonic rift basin; palaeogeography, palaeoclimate and provenance: Neoproterozoic Badami Group, Karnataka, India

An integrated approach of facies analysis, architectural element analysis and geochemistry provides significant insight into the palaeogeography, palaeoclimate and provenances of alluvial sediments in the Neoproterozoic Badami intracratonic rift basin, India. Process-based facies analysis identified twelve facies, grouped into five facies associations that record a palaeoenvironmental setting ranging from screecone – alluvial fan to braided fluvial. Rockfall and debris flow dominate the depositional processes in the screecone – proximal fan settings, whereas streamlet, sieve and sheetflood processes characterize the middle to distal fan palaeogeography. Furthermore, a distal braided fluvial system developed with decreasing depositional slope. Streams within the distal fan had ephemeral flow whereas the braided fluvial setting had semi-perennial to perennial flow. The braided fluvial basin expanded temporally; channels become shallower and wider in response to base profile rise and ultimately drowned under the sea. The poorly sorted clastic deposits of the studied interval are interpreted as a lowstand product. The water table primarily controls spatial variability in flow duration within channels. Nevertheless, temporal water table rise due to a change in climate resulted in persistent flow duration within the fluvial system. The screecone - alluvial fan setting developed on both margins of the east-west trending basin following northerly and southerly palaeoslope respectively. However, associated braided fluvial deposits indicate a westerly dipping palaeoslope, inferred from palaeocurrent directions, which corroborate an intracratonic rift setting. Major and trace element geochemistry and molar A-CN-K plots, CIA and palaeoweathering trends of sandy sediments traced ‘transitional/uplifted continental’, mixed provenances in the north, south and eastern parts of the basin ranging in age from Archaean to Mesoproterozoic. The rifting is inferred to be related to Rodinia supercontinent breakup.

An Improved Techno-Economic Approach to Determination of More Precise Installed Parameter for Small Hydropower Plants

Designing a small hydropower plant (SHPP) necessitates fulfillment of energy and ecological constraints, so a well-defined design flow is of the utmost significance. The main parameters of each SHPP are determined by appropriate techno-economic studies, whereas an improved approach to defining more precise SHPP installed parameter is presented in this paper. The SHPP installed parameter is the ratio of the design flow and averaged perennial flow obtained from the flow duration curve at the planned water intake location. Previous experiences in the design of SHPPs have shown that the SHPP installed parameter has a value in a wide range without the existence of an unambiguous equation for its determination. Therefore, with this aim, the thirty-eight (38) small watercources in the territory of Montenegro, denominated for the construction of SHPPs, have been investigated. SHPPs are divided into two groups depending on the installed capacity and the method of calculating the purchase price of electricity. For both groups, the range of SHPP installed parameter is determined according to the technical and economic criteria: the highest electricity production, the highest income, net present value (NPV), internal rate of return (IRR), and payback period (PB).

Flow regime change alters shredder identity but not leaf litter decomposition in headwater streams affected by severe, permanent drying

Abstract Climate change is altering hydrologic regimes globally. In the Mediterranean climate region of south‐western Australia (SWA), climate drying has caused many perennial streams to switch to intermittent flow regimes. Shifts in flow regime are expected to alter physical and biological processes in streams, including litter decomposition, which is the basis of detrital food webs. Decomposition of jarrah (Eucalyptus marginata) leaves and associated macroinvertebrates, were measured over 320 days in 2018–19 using leaf bags in four headwater streams in SWA. Two streams retained perennial reaches and two were formerly perennial streams that are now intermittent. Pre‐planned comparisons that formed a partial multiple before–after, control–impact design were used to compare the results to an experiment conducted in 1982–83 in some of the same streams when all were perennially flowing. Both experiments used coarse and fine‐mesh bags containing 10 g of dry leaves. In one perennial stream, coarse bags lost more weight than fine bags at the last sampling time only, when shredding caddisflies arrived on the leaf bags. In the other perennial stream, leaf‐mining chironomids entered fine‐mesh bags and accelerated decomposition so that they lost more weight than the coarse‐mesh bags. There was no difference in weight loss between fine and coarse‐mesh leaf bags in the two intermittent streams. In 2018–19, decomposition was slower in dry reaches of intermittent streams than in perennial reaches. Leaf weight loss increased with the resumption of flow in intermittent streams, so that by the end of the experiment, similar amounts of leaf weight had been lost in intermittent and perennial reaches. Thus, although the temporal pattern of decomposition differed between intermittent and perennial reaches, after 320 days, they had reached a similar endpoint. Over similar experimental duration, mean leaf weight remaining in perennial reaches at the end of the experiment did not differ between the 1982–83 study and 2018–19, showing that leaf decomposition had not changed in reaches that retained perennial flow. As mean leaf weight remaining also did not differ between intermittent and perennial streams in 2018–19, leaf decomposition was robust to flow regime change. However, since 1982–83, these streams have lost populations of shredding caddisflies and stoneflies, which were replaced by other shredders (e.g. leaf mining chironomids Stenochironomus sp.), showing that there was some redundancy amongst shredder species. As climate change progresses, drying flow regimes will become commonplace in Mediterranean (and other) climate regions globally. This study indicates that litter decomposition may be maintained as streams transition to intermittency although shredder species may change. However, the impact of shredding species on leaf decomposition varies amongst studies, so effects of the loss of shredder species sensitive to drying may also vary, and in some cases their loss may substantially alter ecosystem processes.