Total Water Discharge Research Articles

Rapid identification of back-flow in three distributaries of Jingjiang Reach, middle Yangtze River, China

Unusual back-flow events occurred in 2015 and 2017 at the near-mainstream ends of the three distributaries of the Jingjiang Reach, middle Yangtze River, China. It is presently challenging to precisely quantify back-flow discharges at river distributary ends where normal-flow discharges are measured chronically. This problem is more complicated at the ends of the three Jingjiang distributaries, each of which is more than 100 km long, and thus favors the generation of different back-flow forms. We use empirical formulae based on the Saint-Venant Equation and the Fall Index Method to quantify impacts on flow discharges at the two ends of each distributary of three key hydrodynamic variables: (1) water discharge at Zhicheng hydrological station, (2) total discharge from the four southwest tributary rivers, and (3) water levels at the two ends of the distributaries. We use the variable control approach to identify the contribution ratios of natural and human driving factors to flow discharges at the two ends of the distributaries during five historical stages. The empirical formulae provide reasonable results, with high values of correlation coefficients (R2 = 0.84 ∼ 0.98) obtained, demonstrating that the total water discharge from the four southwest tributary rivers is negligible. These formulae perform well in reproducing observed flow discharges at the two ends of the distributaries, especially the maximum discharges and cumulative volumes for normal-flow and back-flow events. Three charts are devised for different flow conditions at the two ends, from which back-flow events can be rapidly identified. Before impoundment of the Three Gorges Dam (TGD), riverbed adjustment caused by the lower Jingjiang Cutoff Projects and the Gezhou Dam contributed the most to flow discharge changes (≥50 %) at the near-mainstream ends of the distributaries. Afterwards, precipitation dominated (>60 %). In the future, back-flow events are expected only to occur at Mituosi (i.e., Taipingkou) and Nanxian hydrological stations, for which optimal reservoir operation and water resource utilization could remedy the back-flow crisis. Use of climate models and more advanced technologies such as remote sensing and GIS are recommended to enhance the reliability of predictions.

"FLOODGUARD: An IoT-Powered Real-Time Flash Flood Monitoring and Forecasting System"

Abstract: In recent times, the surge in flooding incidents has become a pressing global issue, inflicting extensive damage on both lives and livelihoods. While floods remain an inevitable force of nature, their devastating impact can be alleviated. With the aid of cutting-edge technologies like the Internet of Things (IoT), proactive flood forecasting has become increasingly feasible. Through the seamless integration of IoT data, populations can receive early warnings and evacuate to safety, safeguarding both lives and valuables. A real-time solution is imperative, leveraging IoT data streams to deliver timely flood alerts. Our study presents an IoT-driven prototype designed to collect hydrological data from rivers, encompassing metrics such as water flow, level, and discharge, alongside meteorological parameters like temperature, humidity, wind speed, and direction. Employing a Long Short-Term Memory (LSTM) model, we analyze and classify collected data based on water discharge, level, rainfall, and temperature, predicting flood events as "no alert," "yellow alert," "orange alert," or "red alert." Given the dynamic nature of rivers, accurately measuring total water discharge poses challenges. To address this, we propose a novel methodology utilizing water flow, sectional area width, and average depth. Furthermore, we tackle the complexities associated with accurately measuring rainfall due to erratic weather conditions. Our system demonstrates robust performance in predicting flood event states, achieving high F1-scores of 97% for "no alert," 97% for "yellow alert," 96% for "orange alert," and 98% for "red alert.

KAJIAN PENANGGULANGAN BANJIR DENGAN PERBAIKAN PENAMPANG SITU PONDOK JAGUNG

Flood mitigation of Situ Pondok Jagung caused by it’s inadequate capacity to handle water, resulting in overflow and localized inundation, this study employed an analytical and simulation modeling approach using SWMM 5.1 software. The modeling process required input data such as Rain Gage, Subctachment, Conduit, Juction, Storage Unit, and Outfall. The analysis and modeling revealed a capacity shortfall, evident from the floodwater levels observed in Situ Pondok Jagung. The analysis and modeling results indicate an excess capacity of the storage capacity, as evidenced by the flood water elevation in Situ Pondok Jagung. Thus, the hydraulic analysis in SWMM 5.1 considers two design conditions: the existing condition with a height of 1.5m, showing a total water discharge of 103,75 m3/s, and a storage volume of 119.250 m2. For the planned condition using trial and error experiment, dredging was performed to a depth of 20cm, and an additional 50cm in height was added to the levee. As a result, the height of Situ Pondok Jagung became 2,2m, with zero overflow, and a storage volume of 174.900 m3. This represents a reduction of 40% and indicates that this planning effort could be considered as an alternative solution.

Water discharge and sediment flux intermittency in the fluvial Escanilla Formation, Spain: Implications for changes in stratigraphic architecture

AbstractWater discharge and sediment flux variations are important parameters controlling the morphodynamic behaviour of rivers. Although quantitative estimates for water discharge and sediment flux variability are well‐constrained for modern rivers, far fewer assessments of flow and sediment flux intermittency in ancient fluvial systems from the rock record are available. In this study, a relationship between water discharge, sediment flux variability and patterns of changing fluvial stratigraphic architecture in the Middle Eocene Escanilla Formation, Spain, is explored. Water discharge intermittency factor (IWF), calculated as a ratio of the total water discharge (over the averaging time period) to the instantaneous channel‐forming water discharge if sustained for the same period, ranges from 0.03 to 0.11 in the high amalgamation intervals and from 0.10 to 0.32 in the low amalgamation intervals. Similarly, the sediment flux intermittency factor (ISF) is estimated to be in the range of 0.008 to 0.01 in the high amalgamation intervals and of 0.01 to 0.03 in the low amalgamation intervals. Consequently, high amalgamation intervals were most probably deposited under more intermittent and short‐lived intense precipitation events while low amalgamation intervals were the result of less intermittent flows spread throughout the year. Overall, these estimates are consistent with values from modern ephemeral rivers typically found in arid to semi‐arid climate and is in agreement with available proxy data for the Middle Eocene climatic context of the studied alluvial system. This highlights an important connection between hydroclimate, river morphodynamics and landscape evolution, and has implications to predict river flow and sediment transport across the Earth's surface in the geological past.

The impact of formation heterogeneity on water discharge and groundwater depletion of an excavated tunnel

The mountainous tectonic zone exhibits high formation heterogeneity, which significantly affects groundwater seepage around the excavated tunnel. Traditional modeling methods that assume the surrounding rock to be a homogeneous field face challenges in accurately predicting and evaluating water discharge within the tunnel. To gain a better understanding of how heterogeneity influences tunnel water discharge, synthetic heterogeneous fields are conducted based on the conceptualization and parameters of the Daxuecheng Tunnel in Chongqing, southwest China. In the heterogeneous modeling, we consider four standard deviations of hydraulic conductivity distribution (0.21, 0.37, 0.55, 0.72) and four dip angles (0°, 30°, 60°, 90°). The results reveal that formation heterogeneity leads to localized instances of significant water inrush and irregular head drawdown distribution, which closely resemble the actual situation compared to the homogeneous model. Generally, the total water discharge into the tunnels increased with increasing heterogeneity and dip angles. Furthermore, the head drawdown in the tunnel region decreased with heterogeneity and increased with dip angles. These findings emphasize the importance of considering formation heterogeneity in tunnel zones and offer valuable guidance for evaluating engineering and environmental challenges in tunnel construction.

TECHNICAL DESIGN OF WELLS (SUMP) AND PUMP REQUIREMENTS IN OPEN PIT MINE DRAINAGE AT PT. MULIA BARATAMA PLAN, LONG BELEH, KEMBANG JANGGUT, KUTAI KARTANEGARA, EAST KALIMANTAN

PT. Rencana Mulia Baratama is one of the companies engaged in coal mining in Long Beleh Village. The area of WIUP OP owned is 3,993 ha with a Production Forest Area of 2,630.4. The drainage system applied at PT. Mulia Baratama's plan is Mine Dewatering, which is by flowing all runoff water into a well (sump) to be pumped out of the mining area which flows into the settling pond. The well is a place that serves to hold a temporary amount of water before being pumped out The actual volume of the well in pit 1 is 58,000 m3. The planned rainfall period based on the 5-year rain reset period is 179.473 mm/day and the duration of rain is 2.4 hours per day. So that the amount of rain intensity calculated by the monobe equation is 37.39 mm/hour. The total water discharge entering the mining site is 58,817,254 m3/day which comes from runoff water discharge of 13,260,552 m3/day and rainwater discharge of 45,556,704 m3/day. The pumping discharge carried out is 462.4 m3/hour using one type of centrifugal pump 200x150 using Rpm 150 so that the total water discharge that can be drained in a day is 7,398.4 m3/day.

Contemporary ice sheet thinning drives subglacial groundwater exfiltration with potential feedbacks on glacier flow.

Observations indicate that groundwater-laden sedimentary aquifers are extensive beneath large portions of the Greenland and Antarctic ice sheets. A reduction in the mechanical loading of aquifers is known to lead to groundwater exfiltration, a discharge of groundwater from the aquifer. Here, we provide a simple expression predicting exfiltration rates under a thinning ice sheet. Using contemporary satellite altimetry observations, we predict that exfiltration rates may reach tens to hundreds of millimeters per year under the fastest thinning parts of the Antarctic Ice Sheet. In parts of West Antarctica, predicted rates of exfiltration would cause the total subglacial water discharge rate to be nearly double what is currently predicted from subglacial basal melting alone. Continued Antarctic Ice Sheet thinning into the future guarantees that the rate and potential importance of exfiltration will only continue to grow. Such an increase in warm, nutrient-laden subglacial water discharge would cause changes in ice sliding, melt of basal ice and marine biological communities.

WATER USE AS A FACTOR IN THE FORMATION OF ECOLOGICAL SAFETY OF THE NICHLAVA RIVER BASIN

The purpose of the article is to determine the level of pollution of the Nichlava River and the structure of water use in its basin from the point of view of forming the ecological security of the region. The following methods were used in the course of the study: evaluation, geoecological analysis, statistical, geoinformation, geochemical and cartographic. Ensuring the ecological safety of a small river basin directly depends on the hydroecological parameters of the river itself. Therefore, studying the pollution of the Nichlava River and the quality of its waters is an important and urgent scientific-practical task.
 Based on the analysis of statistical data from the State Agency of Water Resources of Ukraine, we found that in 2021, 450 thousand m3 of water was withdrawn from natural water bodies in the Nichlava River basin, including 280 thousand m3 from underground water intakes. The used 600 thousand m3 of fresh water, including 260 thousand m3 for drinking and sanitary needs and 340 thousand m3 for production needs. The total water discharge in the Nichlava River basin in 2021 amounted to 660 thousand m3 of water. A total of 650 thousand m3 of wastewater was discharged into the basin's surface water bodies over the year. Including 80 thousand m3 of polluted wastewater and 180 thousand m3 of normatively clean wastewater without wastewater treatment. In 2021, 390 thousand m3 of wastewater was treated at the wastewater treatment plants in the study area. In 2016-2021, 668 thousand m3 of contaminated or insufficiently treated wastewater was discharged into the Nichlava River. Together with the polluted wastewater, 1147 tons of pollutants entered the river. The calculated polluting wastewater discharge coefficient for the Nichlava River basin is 0,12, which indicates not a high concentration of pollutants in the wastewater. However, despite the significant amounts of pollutants discharged into the surface water bodies of the Nichlava River basin, all indicators of the chemical-biological composition of water in the control section of the river meet ecological standards. Therefore, the level of ecological safety in the Nichlava River basin can be considered satisfactory. Promising measures to improve the ecological condition of the river and its basin include optimizing the structure of land use, restoring and preserving coastal protection strips, reconstructing inoperable sewage treatment plants in settlements, and eliminating unauthorized discharges into surface water bodies.
 Therefore, the introduction of effective mechanisms of rational water use in the Nichlava River basin should be a priority area of environmental policy at the regional level of new administrative districts and the local level of territorial communities. The river basin management plan, which must be developed, should include measures to restore the centralized drainage system in small and large settlements, reconstruction of treatment facilities and elimination of unauthorized discharges into surface water bodies.
 Key words: Nichlava River, polluted runoff, water use, water quality.

Optimizing the geothermal potential of tunnel water by separating colder sectional discharges - Case study Brenner Base Tunnel

The use of geothermal energy from tunnels offers an environmentally friendly option for heating and cooling of buildings in the vicinity of the tunnel structure. In the research project “Thermocluster”, the geothermal potential of the Brenner Base Tunnel (BBT) was analysed and the utilization of the low-temperature heat to the city of Innsbruck was evaluated. A possible optimization on the geothermal performance was explored by separating colder sectional discharges from the total tunnel water drainage system. Further, the use of decentralized and centralized heat pumps, as well as heat distribution with different district heating networks (local low temperature heating and cooling networks, low-temperature network, classic district heating network), was investigated using process simulation. The results indicate that an optimization of the temperature of a subset of the total tunnel water discharge is possible. Furthermore, it could be shown that wide fluctuations in the efficiency of the heat pump can be expected. In addition, a rough cost estimation regarding the installation and distribution costs of the tunnel heat with different heat network variants is provided. This shows that the variant using decentralized heat pumps in the buildings and distribution via an anergy network is the most favourable in terms of installation.

CHANGING CLIMATE IN THE POTOHAR REGION- PUNJAB AND ITS EFFECT ON STREAMFLOW: A CASE STUDY OF KANSHI RIVER


 
 
 The current study is to identify and examine the impacts of climate change on the water runoff in the Kanshi catchment of the Potohar Plateau region for 50 years from 1961-2010. Simple linear regression and Pearson correlation were used to assess the correlation coefficient, trend magnitude, and variability of temperature, rainfall, and stream. The results revealed that mean and maximum annual temperature steady and significant increase at the rate of 0.06 °C and 0.053/year during the last two decades. The rainfall pattern was also declined at the rate of -6.821, -0.018, -1.458 and -4.409 mm/year in winter, summer, autumn and spring steadily. Similarly, in August and September, the total water discharge had a significant and negative trend with p values 0.08 and 0.03 during 1991-2010. This substantial and significant change resulted from climate change or increased intercession of anthropogenic activities on the earth's surface.
 
 

Abrupt drainage of Lago Greve, a large proglacial lake in Chilean Patagonia, observed by satellite in 2020

Glacial lakes are increasing in number and extent under a warming climate. Despite demand for lake monitoring and understanding outburst mechanisms, studies of large outburst events are sparse. Here we report an outburst of Lago Greve, a large proglacial lake in Chilean Patagonia. During the event in April–July 2020, the lake level dropped by 18.3 ± 1.2 m and the area decreased by 14.5 ± 0.02 km2. The total water discharge was 3.7 ± 0.2 km3, which is one of the largest glacial lake outbursts ever reported in satellite era. Satellite data indicated the collapse of a bump near the lake outlet triggered the event, by initiating erosion of the bank and bed of the outlet stream. Satellite gravimetry captured a signal of the event, although the magnitude of the corresponding mass change was inconsistent with the drained water mass. Our study demonstrated the potential for observing lake outburst using satellite imagery, altimetry, photogrammetry, and gravimetry.

Surface Water and Groundwater Recharge Modeling in Sunsari District using Integrated SWAT-MODFLOW Model

This study employs an integrated groundwater-surface water (GW-SW) model, using SWAT-MODFLOW, to assess groundwater recharge and withdrawals at a regional scale in eastern Nepal. The model components were calibrated and validated using monthly river flow and hydraulic head data for the 1979-2017 period. Our results demonstrate that the average annual groundwater discharge is 2.43 m3/s. Seasonally, the average groundwater discharge is 2.73 m3/s during Summer and is 2.13 m3/s during winter. We observe that the maximum (6.9 m3/s) and minimum (0.036 m3/s) rates occurred in September-October and March-April, respectively. We also find that the average runoff fraction (i.e., runoff/ precipitation) varied from 0.34 to 0.72, and the ET component varied from 0.24 to 0.547 of the total precipitation within the SWAT model. The yearly fluctuation in TWS varied from ± 9.9% to ± 58% of the total precipitation. The Aquifer thickness varies from 16m to 57 m, and the specific yield in the Sunsari district varied from 0.12 lps to 890 lps. In the southern part, we see the water level declines from 2-4 m from July to August, where the bottom water slowly declines in September. The recharge of 1380 l/sec is observed in the Sapta Koshi area in the Bhabar zone. There is substantial underflow from hills simultaneously, resulting in the total recharge in the Sunsari district of 1.98 MCM/yr. At the same time, the total discharge, including surface, sub-surface, and spring water discharge, is nearly 29.2 MCM/yr. This study shows that the Sunsari district’s water resources have many groundwater and surface water, properly managed for future use.

Application of Mine Dewatering Methods to Reduce Wastewater Pollution in The Environment: Implications for Andesite Mining

Wastewater pollution in mining areas often occurs and becomes a problem in the surrounding groundwater aquifer system. One of the efforts to determine the distribution of wastewater pollution is to calculate the discharge and volume of wastewater. In this study, an open channel in the form of a ditch or commonly referred to as a drainage system is carried out to determine the total water discharge entering the research location, design the dimensions of the sump and design the optimal cross-sectional dimensions of the ditch to overcome the discharge of water that comes out and pollutes the environment. The method used is to make an open channel in the form of a trapezoid to be used around the andesite rock mining site which then drains the mine water to the setlingpond. Efforts to drain the water that has entered the main sump (mine dewatering system) are carried out by making wells, after which the waste water is channeled into the settling pond using a pump. From the results of the study, information was obtained that the total water discharge entering the sump was 235,175 m so that the volume of the sump made was 300 m with dimensions of top area: 20m x 10m, bottom area: 10m x 10m, with a depth of 2m for total water discharge for ditches. 0.0237 m so that the volume of the trench made is 0.228 m.

PERENCANAAN SISTEM AIR BERSIH PADA PEMBANGUNAN TOWER PREMIER APARTEMEN BESS MANSION SURABAYA

Plumbing installation system must be well planned, especially for high rise building. Clean water and waste water networks planning in the Tower Premier BeSS Mansion Surabaya Apartment are designed to serve the occupants needs of clean water. BeSS Mansion Apartement is a high-rise building with ± 86.000 m2area, consist of 3 towers named : Premier Tower and Suite Tower, which have area of 51.700 m2and consist of 44 floors, and Podium Tower which has 34.300 m2 area and consist of 1 semi basement and 9 parking floors. Clean water need is calculated based on the number of occupants and the type of room, which require total clean water discharge of 772.8 m³/day. The pipe diameters of clean water system is designed using 4 inches for main pipes and ¾ inch to 1½ inches for distribution pipes. The ground water tank capacity is 257.6 m³ using two tanks which have a capacity of 144 m³ and 128 m³, while the roof tank has a capacity of 51.52 m³.

Design of Drainage System Coal Mine at PT. Tebo Agung International Site Project, Semambu Village, Sumay District, Tebo Regency, Jambi

Tebo Agung Internasional Ltd is one of the companies in coal mining that employs the open-pit mining method. This sort of method will create a large basin that can accumulate water inside the mining pit. The drainage system is applied at the Pit-1 Site Semambu is mine-dewatering carried out by draining the water into the sump so that it can be pumped out of the mining area and prevent the runoff from coming inside through an open drainage system (ditch). The result of data analysis demonstrated that referring to the daily rainfall in 2010 – 2019 through the distribution of Log Person Type III, the maximum rainfall being planned was 508.019 mm/day within the return period of 5 years. The intensity of rainfall at the research site was 82.5 mm/hour having a rain duration averagely of 3.1 hours/day. Pit-1 Site Semambu had a catchment area around 469,317.15 m2 and a water discharge totally 61,238.81 m3/day derived from rainwater discharge of 48,530.48 m3/day and runoff water discharge 12,708.33 m3/day, whereas the capacity of the temporary accommodating pond (Sump) was 39,539.55 m3. The pump at the research site could not be operated anymore (broken). Accordingly, the recommendation that can be given to the company is changing the broken pumps with 4 units of multi fall 420 pumps having operating speed 1,300 rpm and actual discharge yielded by the pump 871.64 m3/hour. The pump worked for 14 hours/day and the total water discharge that could be produced was 12,202.96 m3/day. Open channel (ditch) at Pit-1 Site Semambu was the only one with accommodated discharge 1.27 m3/second. Thus, the recommendation that could be delivered to optimally prevent the runoff water coming into the mining area is by adding 2 ditches having the capacities of 0.90 m3/second and 0.75 m3/second which have been adjusted to the planned water discharge.

Recent sedimentation in an Amazon tidal tributary: Integrated analysis of morphology and sedimentology

The Xingu River is an important tributary of the Amazon River, contributing 5% of its total water discharge. Nevertheless, it does not contribute substantially to the sediment load. The lower reach of the Xingu River forms a ria, a result of the Holocene sea-level rise. The Xingu is also classified as a tidal river, with tides >1 m at its confluence with the Amazon River. This study evaluated the morphology and sedimentology of the area, correlating both with hydrodynamics to understand the infilling process of the Xingu ria. The study area encompasses a stretch of ~160 km, between the Xingu–Amazon confluence and the narrowing of the fluvial channel. During the season of maximum sediment-discharge of the Amazon River (i.e., Feb 2016), 109 bottom sediment samples were collected. Eleven of the sampling sites were re-sampled during the minimum water-discharge period of both rivers (i.e., Nov 2016). During the maximum water-discharge period of the Amazon River (i.e., Jun 2018), additional water-level measurements were undertaken simultaneously at several locations along the Xingu River. The ria morphology was evaluated on the basis of the bathymetric surveys of the Brazilian Navy (DHN). The results show that the infilling process of the ria has taken place from both the upstream and downstream directions. From upstream, the Xingu River is forming a prominent bayhead delta. From the Xingu-Amazon River confluence, tides have transported Amazon River sediments into the Xingu Ria. There is a central portion of the ria lake with a large cross-sectional area, where relatively small amounts of muddy sediments are accumulating in a quiescent environment. Sands prevail along the lateral margins, where wave action causes bluff erosion and limits fine-sediment deposition. Sands are also common in the bayhead delta and the confluence areas. Results suggest that the sediment input from the Amazon River into the Xingu ria has been reduced over time, likely as result of a reduction in tidally driven flux from the Amazon River into the Xingu River, which has occurred with a gradual increase in the constriction of the confluence as Amazon floodplains prograde.

UAV-based thermal imaging and heat output estimation of a coastal geothermal resource: La Jolla beach, Baja California, Mexico

The exploration of unexploited geothermal resources is required to encourage the use of renewable energy. This study focuses on La Jolla beach, Ensenada, Mexico. The beach hosts a thermal anomaly with temperatures of up to 52 °C at the surface and up to 93 °C at 20 cm depth. The objectives were to: map the thermal anomaly, understand the impact of tides, quantify the thermal water discharge rate and heat output, and discuss a direct use of the energy. The mapping was performed with Unmanned Aerial Vehicles equipped with optical and thermal cameras at two different dates. Additional temperature measurements were performed with a thermocouple, while the total fluid discharge was estimated from flow measurements. A comparison between the campaigns indicated that the highest surface temperature area was more than three times larger in 2019 than in 2018 (259 m2 vs. 69 m2). Such change was due to the tidal range and associated hydrostatic pressure variations. The total thermal water discharge is 330 ± 44 L s−1, which corresponds to an advective heat output of 40.5 ± 5.2 MWt. The use of this energy in a Multi-Effect Distillation desalinization plant can contribute to cover the shortage of freshwater in Ensenada.

The Prut River under Climate Change and Hydropower Impact

Climate change and intensive hydropower development pose serious challenges to the sustainable water supply of natural and social systems. This study’s purpose is to statistically estimate the complex influence of these factors on the Prut River flow. Its methodical approach is based on a comparative analysis of the flow in 1961–1990 and 1991–2018, reflecting the regional climate before and after an intensive global warming onset, and in 1950–1975 and 1980–2017, before and after the construction of the Stanca-Costesti hydropower plant (HPP) on the Prut’s riverbed. The compared statistics include annual, seasonal and monthly averages and trends of climatic and hydrological parameters for each period. Since the 1990s a statistically significant increase has been demonstrated in the basin-wide annual mean, maximum and minimum temperatures, of 1.04, 1.11 and 1.21 °C, respectively. Negative trends of annual precipitation were negligibly small and statistically insignificant in both periods (−2.1 mm and −0.6 mm/year, respectively), with annual totals differing by 1.4 mm. The seasonal transformation and changes of the Prut river flow, showing a small annual increase in the period 1961–1990 and a 1.8% decrease over next decades, are in good agreement with variability patterns of temperature (positive tendencies) and precipitation (negative tendencies). The operation of mean-capacity HPP has no significant impact on the total water discharge downstream, but modifies the seasonal distribution of the river’s streamflow.

Land use planning for mitigation of erosion, sediments, and stabilization of water discharge in the Mamasa Watershed

Watershed Ecosystem is an important part. Activities in a watershed that cause changes in the ecosystem, such as land cover change, especially in the upstream area, can have an impact on downstream areas in the form of change in water flow fluctuation, sediment content and other dissolved materials. The Bakaru reservoir is located in the downstream of Mamasa watershed. In its development, the Bakaru Hydroelectric Power Plant could no longer produce electricity as planned, because of the rapid sediment rate. This research was conducted to determine the amount of erosion, sediment, and water discharge, formulate land use spatial patterns in the watershed. Data analysis was performed by using the SWAT (Soil and Water Assessment Tools) model. Input data needed in the analysis are spatial data, thematic maps such as land use map, soil type map, and Digital Elevation Model data. The results of this study indicate the total erosion of the analysis period is 1,014,576.51 tons/ha/year. The amount of erosion, which is quite high, affects the total sediment (132,852,500.03 tons/year), and the total water discharge generated is around 420,715.54 m3/s. While the output generated using spatial pattern data shows much better results. The total erosion produced was 50,863.86 tons/ha/year, while the total sediment amounted to 14,903,914.25 tons/year and water discharge 48,697.00 m3/s. Based on these results, it can be said that if land use is adjusted to a predetermined spatial pattern, then the results of erosion and sediment can be tolerated, and water discharge can be maximized. The direction of optimizing land cover, mainly forest land cover, is in accordance with the proposed spatial patterns that have been set in each district. The implementation of the direction of optimizing forest land cover adjusted to the spatial pattern is expected to be a strategic alternative in maintaining the erosion balance in the upstream, sediment, and water discharge at each river outlet.

Runoff‐generated debris flows: Observation of initiation conditions and erosion–deposition dynamics along the channel at Cancia (eastern Italian Alps)

AbstractIn the Dolomitic region, abundant coarse hillslope sediment is commonly found at the toe of rocky cliffs. Ephemeral channels originate where lower permeability bedrock surfaces concentrate surface runoff. Debris flows initiate along such channels following intense rainfall and determine the progressive erosion and deepening of the channels. Sediment recharge mechanisms include rock fall, dry ravel processes and channel‐bank failures. Here we document debris flow activity that took place in an active debris flow basin during the year 2015. The Cancia basin is located on the southwestern slope of Mount Antelao (3264 m a.s.l.) in the dolomitic region of the eastern Italian Alps. The 2.5 km2 basin is incised in dolomitic limestone rocks. The data consist of repeated topographic surveys, distributed rainfall measurements, time‐lapse (2 s) videos of two events and pore pressure measurements in the channel bed. During July and August 2015, two debris flow events occurred, following similarly intense rainstorms. We compared rainfall data to existing rainfall triggering thresholds and simulated the hydrological response of the headwater catchment with a distributed model in order to estimate the total and peak water discharge. Our data clearly illustrate how debris entrainment along the channel is the main contributor to the overall mobilized volume and that erosion is dominant when the channel slope exceeds 16°. Further downstream, sediment accumulation and depletion occurred alternately for the two successive events, indicating that sediment availability along the channel also influences the flow behaviour along the prevailing‐transport reach. The comparison between monitoring data, topographical analysis and hydrological simulation allows the estimation of the average solid concentration of the two events and suggests that debris availability has a significant influence on the debris flow volume. © 2020 John Wiley & Sons, Ltd.