scholarly journals Contrasting Differences in Responses of Streamflow Regimes between Reforestation and Fruit Tree Planting in a Subtropical Watershed of China

Forests ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 212 ◽  
Author(s):  
Zhipeng Xu ◽  
Wenfei Liu ◽  
Xiaohua Wei ◽  
Houbao Fan ◽  
Yizao Ge ◽  
...  
Keyword(s):  
Flow Regime ◽  
Fruit Tree ◽  
High Flow ◽  
Tree Planting ◽  
Low Flow ◽  
Jiangxi Province ◽  
Negative Effects ◽  
Flow Duration ◽  
Low Flows ◽  
High Flows

Fruit tree planting is a common practice for alleviating poverty and restoring degraded environment in developing countries. Yet, its environmental effects are rarely assessed. The Jiujushui watershed (261.4 km2), located in the subtropical Jiangxi Province of China, was selected to assess responses of several flow regime components on both reforestation and fruit tree planting. Three periods of forest changes, including a reference (1961 to 1985), reforestation (1986 to 2000) and fruit tree planting (2001 to 2016) were identified for assessment. Results suggest that the reforestation significantly decreased the average magnitude of high flow by 8.78%, and shortened high flow duration by 2.2 days compared with the reference. In contrast, fruit tree planting significantly increased the average magnitude of high flow by 27.43%. For low flows, reforestation significantly increased the average magnitude by 46.38%, and shortened low flow duration by 8.8 days, while the fruit tree planting had no significant impact on any flow regime components of low flows. We conclude that reforestation had positive impacts on high and low flows, while to our surprise, fruit tree planting had negative effects on high flows, suggesting that large areas of fruit tree planting may potentially become an important driver for some negative hydrological effects in our study area.

scholarly journals Hydrological Foundation as a Basis for a Holistic Environmental Flow Assessment of Tropical Highland Rivers in Ethiopia

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 547 ◽  
Author(s):  
Wubneh B. Abebe ◽  
Seifu A. Tilahun ◽  
Michael M. Moges ◽  
Ayalew Wondie ◽  
Minychl G. Derseh ◽  
...  
Keyword(s):  
Flow Regime ◽  
Current Flow ◽  
Environmental Flow ◽  
High Flow ◽  
Low Flow ◽  
Trend Test ◽  
Floodplain Wetlands ◽  
Low Flows ◽  
Flow Components ◽  
Large Floods

The sustainable development of water resources includes retaining some amount of the natural flow regime in water bodies to protect and maintain aquatic ecosystem health and the human livelihoods and wellbeing dependent upon them. Although assessment of environmental flows is now occurring globally, limited studies have been carried out in the Ethiopian highlands, especially studies to understand flow-ecological response relationships. This paper establishes a hydrological foundation of Gumara River from an ecological perspective. The data analysis followed three steps: first, determination of the current flow regime—flow indices and ecologically relevant flow regime; second, naturalization of the current flow regime—looking at how flow regime is changing; and, finally, an initial exploration of flow linkages with ecological processes. Flow data of Gumara River from 1973 to 2018 are used for the analysis. Monthly low flow occurred from December to June; the lowest being in March, with a median flow of 4.0 m3 s−1. Monthly high flow occurred from July to November; the highest being in August, with a median flow of 236 m3 s−1. 1-Day low flows decreased from 1.55 m3 s−1 in 1973 to 0.16 m3 s−1 in 2018, and 90-Day (seasonal) low flow decreased from 4.9 m3 s−1 in 1973 to 2.04 m3 s−1 in 2018. The Mann–Kendall trend test indicated that the decrease in low flow was significant for both durations at α = 0.05. A similar trend is indicated for both durations of high flow. The decrease in both low flows and high flows is attributed to the expansion of pump irrigation by 29 km2 and expansion of plantations, which resulted in an increase of NDVI from 0.25 in 2000 to 0.29 in 2019. In addition, an analysis of environmental flow components revealed that only four “large floods” appeared in the last 46 years; no “large flood” occurred after 1988. Lacking “large floods” which inundate floodplain wetlands has resulted in early disconnection of floodplain wetlands from the river and the lake; which has impacts on breeding and nursery habitat shrinkage for migratory fish species in Lake Tana. On the other hand, the extreme decrease in “low flow” components has impacts on predators, reducing their mobility and ability to access prey concentrated in smaller pools. These results serve as the hydrological foundation for continued studies in the Gumara catchment, with the eventual goal of quantifying environmental flow requirements.

Effect of l-menthol on laryngeal receptors

1991 ◽  
Vol 70 (2) ◽  
pp. 788-793 ◽  
Author(s):  
F. B. Sant'Ambrogio ◽  
J. W. Anderson ◽  
G. Sant'Ambrogio
Keyword(s):  
Statistical Significance ◽  
Upper Airway ◽  
High Flow ◽  
Low Flow ◽  
Lower Flow ◽  
Low Flows ◽  
Cold Receptors ◽  
Anesthetized Dogs ◽  
High Flows ◽  
Similar Decrease

We have studied the effect of l-menthol on laryngeal receptors. Experiments have been conducted in 11 anesthetized dogs that breathed through a tracheostomy. We have recorded the activity of 23 laryngeal cold receptors and 19 mechanoreceptors. Constant flows of air, 15-50 ml/s (low) and 100-150 ml/s (high), passing for 10 s through the isolated upper airway in the expiratory direction, lowered laryngeal temperature and activated the cold receptors. This cold-induced discharge promptly ceased upon withdrawal of the airflow. Addition of l-menthol to the airflow evoked, for a similar decrease in temperature, a greater peak activation of the cold receptors than airflow alone (low flows 164%, high flows 111%); statistical significance was reached only for the lower flow. This activity outlasted the cessation of airflow by 30-120 s, even at a time when laryngeal temperature had returned to control (low flow 237%, high flow 307% of similar trials with airflow alone). Four laryngeal cold receptors were also tested with l-menthol added to a warm, humidified airflow that did not change laryngeal temperature; all of them were stimulated with a long-lasting discharge. Nine cold receptors were also tested with d-neomenthol and d-isomenthol; both isomers stimulated the receptors. None of the 19 mechano-receptors tested was affected by l-menthol. We conclude that l-menthol constitutes a specific stimulant of laryngeal cold receptors and could provide a useful tool for the study of their reflex effects.

scholarly journals Future shifts in extreme flow regimes in Alpine regions

2019 ◽  
Vol 23 (11) ◽  
pp. 4471-4489 ◽  
Author(s):  
Manuela I. Brunner ◽  
Daniel Farinotti ◽  
Harry Zekollari ◽  
Matthias Huss ◽  
Massimiliano Zappa
Keyword(s):  
Time Series ◽  
Frequency Analysis ◽  
Flow Regimes ◽  
High Flow ◽  
Discharge Time ◽  
Climate Conditions ◽  
Flow Duration ◽  
High Flows ◽  
Flow Duration Curves ◽  
Extreme Flow

Abstract. Extreme low and high flows can have negative economic, social, and ecological effects and are expected to become more severe in many regions due to climate change. Besides low and high flows, the whole flow regime, i.e., annual hydrograph comprised of monthly mean flows, is subject to changes. Knowledge on future changes in flow regimes is important since regimes contain information on both extremes and conditions prior to the dry and wet seasons. Changes in individual low- and high-flow characteristics as well as flow regimes under mean conditions have been thoroughly studied. In contrast, little is known about changes in extreme flow regimes. We here propose two methods for the estimation of extreme flow regimes and apply them to simulated discharge time series for future climate conditions in Switzerland. The first method relies on frequency analysis performed on annual flow duration curves. The second approach performs frequency analysis of the discharge sums of a large set of stochastically generated annual hydrographs. Both approaches were found to produce similar 100-year regime estimates when applied to a data set of 19 hydrological regions in Switzerland. Our results show that changes in both extreme low- and high-flow regimes for rainfall-dominated regions are distinct from those in melt-dominated regions. In rainfall-dominated regions, the minimum discharge of low-flow regimes decreases by up to 50 %, whilst the reduction is 25 % for high-flow regimes. In contrast, the maximum discharge of low- and high-flow regimes increases by up to 50 %. In melt-dominated regions, the changes point in the other direction than those in rainfall-dominated regions. The minimum and maximum discharges of extreme regimes increase by up to 100 % and decrease by less than 50 %, respectively. Our findings provide guidance in water resource planning and management and the extreme regime estimates are a valuable basis for climate impact studies. Highlights Estimation of 100-year low- and high-flow regimes using annual flow duration curves and stochastically simulated discharge time series Both mean and extreme regimes will change under future climate conditions. The minimum discharge of extreme regimes will decrease in rainfall-dominated regions but increase in melt-dominated regions. The maximum discharge of extreme regimes will increase and decrease in rainfall-dominated and melt-dominated regions, respectively.

scholarly journals A large sample analysis of European rivers on seasonal river flow correlation and its physical drivers

2019 ◽  
Vol 23 (1) ◽  
pp. 73-91 ◽  
Author(s):  
Theano Iliopoulou ◽  
Cristina Aguilar ◽  
Berit Arheimer ◽  
María Bermúdez ◽  
Nejc Bezak ◽  
...  
Keyword(s):  
River Flow ◽  
Frequency Estimation ◽  
Low Flow ◽  
Time Lags ◽  
Low Flows ◽  
Flow Formation ◽  
Gaussian Probability Distribution ◽  
High Flows ◽  
Seasonal Correlation ◽  
Seasonal Streamflow

Abstract. The geophysical and hydrological processes governing river flow formation exhibit persistence at several timescales, which may manifest itself with the presence of positive seasonal correlation of streamflow at several different time lags. We investigate here how persistence propagates along subsequent seasons and affects low and high flows. We define the high-flow season (HFS) and the low-flow season (LFS) as the 3-month and the 1-month periods which usually exhibit the higher and lower river flows, respectively. A dataset of 224 rivers from six European countries spanning more than 50 years of daily flow data is exploited. We compute the lagged seasonal correlation between selected river flow signatures, in HFS and LFS, and the average river flow in the antecedent months. Signatures are peak and average river flow for HFS and LFS, respectively. We investigate the links between seasonal streamflow correlation and various physiographic catchment characteristics and hydro-climatic properties. We find persistence to be more intense for LFS signatures than HFS. To exploit the seasonal correlation in the frequency estimation of high and low flows, we fit a bi-variate meta-Gaussian probability distribution to the selected flow signatures and average flow in the antecedent months in order to condition the distribution of high and low flows in the HFS and LFS, respectively, upon river flow observations in the previous months. The benefit of the suggested methodology is demonstrated by updating the frequency distribution of high and low flows one season in advance in a real-world case. Our findings suggest that there is a traceable physical basis for river memory which, in turn, can be statistically assimilated into high- and low-flow frequency estimation to reduce uncertainty and improve predictions for technical purposes.

scholarly journals Accounting for environmental flow requirements in global water assessments

2014 ◽  
Vol 18 (12) ◽  
pp. 5041-5059 ◽  
Author(s):  
A. V. Pastor ◽  
F. Ludwig ◽  
H. Biemans ◽  
H. Hoff ◽  
P. Kabat
Keyword(s):  
Flow Regime ◽  
Environmental Flows ◽  
Environmental Flow ◽  
Ecological Condition ◽  
Freshwater Ecosystems ◽  
Low Flow ◽  
Human Needs ◽  
High Flows ◽  
The Mean ◽  
Global Vegetation

Abstract. As the water requirement for food production and other human needs grows, quantification of environmental flow requirements (EFRs) is necessary to assess the amount of water needed to sustain freshwater ecosystems. EFRs are the result of the quantification of water necessary to sustain the riverine ecosystem, which is calculated from the mean of an environmental flow (EF) method. In this study, five EF methods for calculating EFRs were compared with 11 case studies of locally assessed EFRs. We used three existing methods (Smakhtin, Tennant, and Tessmann) and two newly developed methods (the variable monthly flow method (VMF) and the Q90_Q50 method). All methods were compared globally and validated at local scales while mimicking the natural flow regime. The VMF and the Tessmann methods use algorithms to classify the flow regime into high, intermediate, and low-flow months and they take into account intra-annual variability by allocating EFRs with a percentage of mean monthly flow (MMF). The Q90_Q50 method allocates annual flow quantiles (Q90 and Q50) depending on the flow season. The results showed that, on average, 37% of annual discharge was required to sustain environmental flow requirement. More water is needed for environmental flows during low-flow periods (46–71% of average low-flows) compared to high-flow periods (17–45% of average high-flows). Environmental flow requirements estimates from the Tennant, Q90_Q50, and Smakhtin methods were higher than the locally calculated EFRs for river systems with relatively stable flows and were lower than the locally calculated EFRs for rivers with variable flows. The VMF and Tessmann methods showed the highest correlation with the locally calculated EFRs (R2=0.91). The main difference between the Tessmann and VMF methods is that the Tessmann method allocates all water to EFRs in low-flow periods while the VMF method allocates 60% of the flow in low-flow periods. Thus, other water sectors such as irrigation can withdraw up to 40% of the flow during the low-flow season and freshwater ecosystems can still be kept in reasonable ecological condition. The global applicability of the five methods was tested using the global vegetation and the Lund-Potsdam-Jena managed land (LPJmL) hydrological model. The calculated global annual EFRs for fair ecological conditions represent between 25 and 46% of mean annual flow (MAF). Variable flow regimes, such as the Nile, have lower EFRs (ranging from 12 to 48% of MAF) than stable tropical regimes such as the Amazon (which has EFRs ranging from 30 to 67% of MAF).

scholarly journals Long term prediction of flood occurrence

2016 ◽  
Vol 373 ◽  
pp. 189-192 ◽  
Author(s):  
Cristina Aguilar ◽  
Alberto Montanari ◽  
María José Polo
Keyword(s):  
Flow Regime ◽  
River Flow ◽  
Research Question ◽  
Flood Frequency ◽  
High Flow ◽  
Low Flow ◽  
Physical Explanation ◽  
Po River ◽  
Flood Season

Abstract. How long a river remembers its past is still an open question. Perturbations occurring in large catchments may impact the flow regime for several weeks and months, therefore providing a physical explanation for the occasional tendency of floods to occur in clusters. The research question explored in this paper may be stated as follows: can higher than usual river discharges in the low flow season be associated to a higher probability of floods in the subsequent high flow season? The physical explanation for such association may be related to the presence of higher soil moisture storage at the beginning of the high flow season, which may induce lower infiltration rates and therefore higher river runoff. Another possible explanation is persistence of climate, due to presence of long-term properties in atmospheric circulation. We focus on the Po River at Pontelagoscuro, whose catchment area amounts to 71 000 km2. We look at the stochastic connection between average river flows in the pre-flood season and the peak flows in the flood season by using a bivariate probability distribution. We found that the shape of the flood frequency distribution is significantly impacted by the river flow regime in the low flow season. The proposed technique, which can be classified as a data assimilation approach, may allow one to reduce the uncertainty associated to the estimation of the flood probability.

scholarly journals Topography significantly influencing low flows in snow-dominated watersheds

2017 ◽  
Author(s):  
Qiang Li ◽  
Xiaohua Wei ◽  
Xin Yang ◽  
Krysta Giles-Hansen ◽  
Mingfang Zhang ◽  
...  
Keyword(s):  
Regression Models ◽  
Low Flow ◽  
Mean Flow ◽  
Slope Length ◽  
Low Flows ◽  
Slope Length Factor ◽  
High Flows ◽  
Flow Variables ◽  
Characterization Index

Abstract. Watershed topography plays an important role in determining the spatial heterogeneity of ecological, geomorphological, and hydrological processes. Few studies have quantified the role of topography on various flow variables. In this study, 28 watersheds with snow-dominated hydrological regimes were selected with daily flow records from 1989 to 1996. The watersheds are located in the Southern Interior of British Columbia, Canada and range in size from 2.6 to 1,780 km2. For each watershed, 22 topographic indices (TIs) were derived, including those commonly used in hydrology and other environmental fields. Flow variables include annual mean flow (Qmean), Q10%, Q25%, Q50%, Q75%, Q90%, and annual minimum flow (Qmin), where Qx% is defined as flows that at the percentage (x) occurred in any given year. Factor analysis (FA) was first adopted to exclude some redundant or repetitive TIs. Then, stepwise regression models were employed to quantify the relative contributions of TIs to each flow variable in each year. Our results show that topography plays a more important role in low flows than high flows. However, the effects of TIs on flow variables are not consistent. Our analysis also determines five significant TIs including perimeter, surface area, openness, terrain characterization index, and slope length factor, which can be used to compare watersheds when low flow assessments are conducted, especially in snow-dominated regions.

scholarly journals Mekong River flow and hydrological extremes under climate change

2016 ◽  
Vol 20 (7) ◽  
pp. 3027-3041 ◽  
Author(s):  
Long Phi Hoang ◽  
Hannu Lauri ◽  
Matti Kummu ◽  
Jorma Koponen ◽  
Michelle T. H. van Vliet ◽  
...  
Keyword(s):  
Climate Change ◽  
River Flow ◽  
High Flow ◽  
Mekong River ◽  
Low Flow ◽  
Future Climate Change ◽  
Climate Projections ◽  
Low Flows ◽  
Hydrological Extremes ◽  
Hydrological Impact

Abstract. Climate change poses critical threats to water-related safety and sustainability in the Mekong River basin. Hydrological impact signals from earlier Coupled Model Intercomparison Project phase 3 (CMIP3)-based assessments, however, are highly uncertain and largely ignore hydrological extremes. This paper provides one of the first hydrological impact assessments using the CMIP5 climate projections. Furthermore, we model and analyse changes in river flow regimes and hydrological extremes (i.e. high-flow and low-flow conditions). In general, the Mekong's hydrological cycle intensifies under future climate change. The scenario's ensemble mean shows increases in both seasonal and annual river discharges (annual change between +5 and +16 %, depending on location). Despite the overall increasing trend, the individual scenarios show differences in the magnitude of discharge changes and, to a lesser extent, contrasting directional changes. The scenario's ensemble, however, shows reduced uncertainties in climate projection and hydrological impacts compared to earlier CMIP3-based assessments. We further found that extremely high-flow events increase in both magnitude and frequency. Extremely low flows, on the other hand, are projected to occur less often under climate change. Higher low flows can help reducing dry season water shortage and controlling salinization in the downstream Mekong Delta. However, higher and more frequent peak discharges will exacerbate flood risks in the basin. Climate-change-induced hydrological changes will have important implications for safety, economic development, and ecosystem dynamics and thus require special attention in climate change adaptation and water management.

Exploring natural and induced drivers in the Magdalena River discharge impacting the Ciénaga Grande de Santa Marta coastal-lagoon ecosystem

2021 ◽  
Author(s):  
Santiago Gómez-Dueñas ◽  
Allen Bateman ◽  
Germán Santos ◽  
Raúl Sosa
Keyword(s):  
Coastal Lagoon ◽  
Southern Oscillation ◽  
A Priori ◽  
Open Water ◽  
Low Flow ◽  
Enso Events ◽  
Low Flows ◽  
Rain Season ◽  
Discharge Regime ◽  
High Flows

<p>Magdalena's river basin represents a quarter of Colombia's surface, yet neighbouring ecosystems remain ignored while enduring unacceptable environmental conditions. At its outlet in the Caribbean Sea, several channels link it to Cienaga Grande de Santa Marta (CGSM), a deltaic coastal-lagoon ecosystem (4200 km<sup>2</sup>) from which around 15 to 20 % are water bodies. According to several studies, Magdalena River's overflows represent its primary freshwater source. However, the recorded discharge has gradually reduced, though the basin's rainfall shows a rising tendency. Additional discharge measurements close to the outlet evidenced that it was even lesser than records upstream counterintuitively. Consequently, the energy gradient from the river to the sea through the ecosystem is reversing more frequently. That has resulted in a continuous salinisation process of the lagoons, diminishment of the mangrove forest and lagoons extension, fauna migration and low water quality. This research aims to elaborate on the Magdalena River's outlet discharges vulnerabilities in Colombia, thus providing better insight into impact-based decision-making. </p><p>Results suggest that the discharge regime responds to the El Niño Southern Oscillation (ENSO) phenomenon as it controls the country's dry/rain season. Further analysis indicates that a) low flows relate to El Niño periods and high flows to La Niña; b) the flow duration curve's slope is getting milder, meaning that high flows are decreasing whereas low flows are increasing; c) extreme discharges are getting smoother, and less disperse so that high and low flow peaks are within a smaller range; d) the dispersion diminishes radically during severe El Niño events, and e) although a priori the assumption is that the more severe El Niño events might bring lower discharge values, the minimum values recorded are more significant than in neutral ENSO conditions. </p><p>Moreover, extreme discharge values during ENSO events, despite their severity, tended to have a horizontal asymptote that suggests human-driven control upstream, especially during El Niño periods. The Magdalena basin holds Colombia's hydropower network representing more than 70% of its electricity supply distributed in 33 operating plants. On the one hand, it is clear that during El Niño, the plants guarantee a minimum discharge downstream, as it is when the National Hydrometeorological Agency only considers drought protocols. However, during neutral ENSO conditions, the flows are not controlled and thus, impacts downstream arise. On the other hand, reservoirs have increased evaporation due to a large accumulated open water surface (611 km<sup>2</sup> in total). Results show that water loss represents 40% to 80% of the current average discharge at the outlet (7000 m<sup>3</sup>/s), adding to the ecosystem depletion. The results urge decision-makers to reconsider the drought protocols applying an impact-based approach.</p>

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