Catchment Boundaries Research Articles

The impact of digital elevation model data sources on identifying catchment boundary in Vietnam

The impact of digital elevation model data sources on identifying catchment boundary in Vietnam

Identifying hydrologic reference stations to understand changes in water resources across Vietnam - a data-driven approach

Among the impacts of climate change and variabilities, change in the terrestrial water cycle has been investigated extensively due to the importance of water resources to the Earth System. The detection and attribution of changes in river flows, however, are usually complicated by the impacts of on-ground human activities such as urbanization or dam construction that have altered flow regimes. As a result, hydrological reference stations – gauges measuring river flows of catchments that are unregulated - have been identified in many countries to provide streamflow records that are suitable for climate studies. Such a network, to the best of our knowledge, has not been promoted widely in Vietnam, making it difficult to determine the actual impact of climate change and variability to river flow regimes at the national scale. To address this limitation, this study uses a data-driven approach to identify stations that have not been influenced substantially by human activities for Vietnam. Specifically, we have carefully assessed streamflow records at 68 locations that are not influenced by tidal regime to identify stations with relatively good data quality. The drainage area associated with each of these stations was then delineated following international standards, and then used to identify catchments that were not associated with large dams. The catchment boundary was also used to extract land surface information, available through an ensemble of different satellite-based data products, to further identify catchments that are not featured by large urban areas, or experienced a substantial change in land cover during the 2000-2019 period. Using these criteria, this study suggested two subsets of stations distributed across the countries, providing a good starting point for future investigations into the impacts of climate change on water resources in Vietnam. The investigation also suggests that more investments are required to maintain and expand the hydrologic reference network for Vietnam.

Hydrogeological Investigations in Basement Terrains Using Geological, Geomor-Phological and Geophysical Methods, Western Hamissana Area, NE Sudan

This study aims at identifying target zones for groundwater exploration in basement terrains using geological, geomorphological, and geoelectrical methods. The study area is located on the northwestern side of the Red Sea Hills in the western Hamissana area. It is part of the Arabian Nubian Shield (ANS), which dates to the Pan-African Era. The study area is covered by Precambrian basement rocks which are overlain by alluvial deposits. The climate in the region is arid. As a result, severe water shortage is experienced. The geological and geomorphological investigations were carried out to locate potential sites for groundwater prospecting. On this basis, three categories of groundwater potential zones were delineated as good, moderate, or poor. The electrical resistivity method using vertical electrical sounding (VES) technique was used to determine the vertical geological profile of the study area. The sequence was revealed to consist of four zones: a high-resistance unsaturated zone, an intermediate-resistance water-bearing formation, a low-resistance wet weathered basement, and high-resistance fresh basement rock. Catchment boundaries were delineated using digital elevation models, and potential locations for surface and subsurface dams were proposed to improve the groundwater recharge.

Definition of headwater catchment boundaries

Definition of headwater catchment boundaries

Hydrological Modeling of Karst Watershed Containing Subterranean River Using a Modified SWAT Model: A Case Study of the Daotian River Basin, Southwest China

Karst watershed refers to the total range of surface and underground recharge areas of rivers (including subterranean rivers and surface rivers) in karst areas. Karst water resources, as the primary source of domestic water supply in southwest China, are vital for the social and economic development of these regions. It is greatly significant to establish a high-precision hydrological model of karst watershed for guiding water resources management in karst areas. Choosing the Daotian river basin in the Wumeng Mountains of Southwest China as the study area, this paper proposed a method for simplifying karst subterranean rivers into surface rivers by modifying the digital elevation model (DEM) based on a field survey and tracer test. This method aims to solve the inconsistency between the topographical drainage divides and actual catchment boundaries in karst areas. The Soil and Water Assessment Tool (SWAT) model was modified by replacing the single-reservoir model in the groundwater module with a three-reservoir model to depict the constraints of multiple media on groundwater discharge in the karst system. The results show that the catchment areas beyond topographic watershed were effectively identified after simplifying subterranean rivers to surface rivers based on the modified DEM data, which ensured the accuracy of the basic model. For the calibration and two validation periods, the Nash–Sutcliffe efficiencies (NSE) of the modified SWAT model were 0.87, 0.83, and 0.85, respectively, and R2 were 0.88, 0.84, and 0.86, respectively. The NSE of the modified SWAT model was 0.09 higher than that of the original SWAT model in simulating baseflow, which effectively improved the simulation accuracy of daily runoff. In addition, the modified SWAT model had a lower uncertainty within the same parameter ranges than the original one. Therefore, the modified SWAT model is more applicable to karst watersheds.

Flow Behavior of Boyong River as Revealed by Long-term Hydro-monitoring System

Boyong River is one of many rivers originating from Mt. Merapi, flows across three autonomy administrative of Sleman Regency, Yogyakarta City, and Bantul Regency. The river experiences flood in the form of lava flow several times, and the 1994 and 2010 occurrences were considered the biggest ones along with the river history. In line with the rapid development of information and communication technology, efforts to develop the early warning system due to the Mt. Merapi disaster have been implemented by the Hydraulic Laboratory of Gadjah Mada University 2006. This paper presents the study results of Boyong River flow behavior by analyzing the data obtained from the monitoring system. The Gemawang Weir at Boyong River was selected as the river control point understudy; those include the catchment boundary, the catchment characteristics, and the hydraulic features. Monitoring equipment consists of an automatic water level recorder (AWLR), the flow visualization using a Brinno camera, and the hydrophone monitoring system. The flow hydrograph characteristics and its corresponding sediment transport rate are considered two parameters for identifying the flow behavior. The results show that the precursive and recession times of the flood hydrograph are about 1-3 hours and 3.5-5 hours, respectively.

Vertical Migration of Adult Plecoptera and Trichoptera above Forested Headwater Streams.

Simple SummaryStream insects are essential components of aquatic and terrestrial ecosystems, but fewer studies have examined the terrestrial stage compared to the aquatic stage. Most adult stream insects are flight capable, which allows for short- and long-distance movements away from the stream channel into riparian or upland habitats. This study examined if adult stream insects migrate vertically into riparian forest canopies above the stream. We found a meaningful number of adult Trichoptera and Plecoptera in the forest canopy above the stream that was comparable to horizontal migrations. This result demonstrated that adult stream insects utilize riparian forest canopies and that numerous avenues for additional basic and applied research on terrestrial–aquatic linkages exist. Discovering how riparian canopy habitats are important for stream insects and how stream insects are linked to canopy ecosystems can inform restoration and conservation actions.Stream insects are essential components of aquatic and terrestrial ecosystem structure and function. Terrestrial stages are important components of terrestrial food webs, and flight-capable individuals are responsible for long-distance dispersal. Horizontal migrations by flying or crawling adults away from stream channels that link insects to riparian food webs and movements across catchment boundaries are well established through empirical research, but studies examining vertical migration of adult stream insects into forest canopies are generally lacking. This study focused on differences in adult Plecoptera and Trichoptera abundance at ground level versus the riparian canopy and differences in abundances among summer and autumn sampling periods to empirically demonstrate use of canopy ecosystems by stream insects. Malaise traps at ground level and canopy traps placed 8 to 10 m above the stream at four sites in the Mosquito Creek watershed (Pennsylvania) were used to examine vertical migration. Larval assemblages were collected and compared to adult assemblage to investigate patterns of local migration in the catchment. We found significantly more stream insects at ground level than in the forest canopy for Trichoptera, Plecoptera, and all individual plecopteran families, but a meaningful number of individuals were found in the riparian canopy. Canopy abundances were similar to abundances captured in adjacent ground-level habitats in other studies. Comparisons of adult and larval abundances among sites, taxa, and stages indicated site- and taxon-specific patterns for vertical movement into riparian canopies. Demonstrating that adult stream insects utilize riparian forest canopies indicates that riparian forest conservation should be prioritized over reforestation and that several potential research questions exist to inform riparian management.

Use of Isotope Technique in Groundwater Investigation around Erbil City- Northern Iraq

The fundamental characteristics of environmental isotopes in water resources management is dependable on the nature of geographical region of the catchment boundaries. The method of applying different isotopes has a main character in quantity and quality estimations of water resources that sometimes cannot be achieved by old techniques. Nowadays the detailed inquiry of surface water or ground water difficulties can practically have been explained against the support of performing the isotopes. The present study assembled some investigations and applications on the environmental isotopes that predict the water management systems in different catchment areas and implementing the isotope techniques in Kurdistan region of Iraq. This should help us to solve many problems of surface and ground water such as the recognition a source of ground water, ground water dating, problems of ground water contamination, trace the direction and velocity of flow, the interaction of surface water with ground water, physical transportation link between different aquifers, some characteristics of an aquifer and renewability of water. The objectives of this study are to implicate and investigate on the most intensive science of environmental isotope in different catchment areas of Kurdistan region in northern Iraq. The data were taken by (Dana,2016) for different springs and wells in the region starting from Haji-Omaran to Barzan. There are no meteorological or hydrographic measuring stations. The ground water compositions of 10 wells and 12 springs were illustrates that the seasonal does not conclusive a part while the assumptions would be modified for the precipitation data. The results show that, groundwater saves the 18O and deuterium (D) content out of which they were formed. The isotope contents of most groundwater lie somewhere near the local respective meteoric water line (MWL). Whereas, the proportionality pf high degree in deuterium surplus (d) is about 10 which is representative for the Mediterranean Sea region. also, the high concentration of isotopes was taken place at Haji-Omaran and Jundian w that about 8.93 and 8.37 degrees respectively. This is leads to offer the possibility with a relatively small financial expense to use isotopic hydrological methods to explore the underground water balance in northern Iraq.

Effect of DEM-smoothing and -aggregation on topographically-based flow directions and catchment boundaries

It is generally assumed that, in humid climates, the groundwater table is a subdued copy of the surface topography. However, the general groundwater table is unlikely to be affected by the microtopography as seen in high-resolution Digital Elevation Models (DEMs). So far, there has been little guidance on the best resolution DEM to use to determine the shape of the water table or the direction of shallow groundwater flow in headwater catchments. We, therefore, looked at the effects of DEM-smoothing and -aggregation on the calculated flow directions and derived catchment boundaries, and identified areas and landscape features for which the calculated flow directions are particularly sensitive to DEM smoothing or aggregation. For > 40 % of the area of the Krycklan study catchment, the calculated flow directions depend strongly on the degree of smoothing or aggregation of the DEM. The four main landscape features for which DEM smoothing or aggregation strongly affected the calculated flow directions were: local slopes in the opposite direction of the general slope, flat areas, ridges, and incised streambanks. To determine the effects of the changing flow directions on the derived catchment boundaries for the smoothed and aggregated DEMs, we calculated the drainage area for 40 locations, representing the outlets of catchments of varying sizes. The shape and size of the catchments of first-order streams were most affected by the processing of the DEM. These streams were often almost completely smoothed out during the DEM preprocessing steps. These shifts in catchment boundaries and drainage area would have a large effect on the water balance. This study thus highlights the need to carefully consider the effects of DEM smoothing or -aggregation on the calculated flow directions and drainage areas.

An alternative method for groundwater recharge estimation in karst

Aquifers with time variant catchment boundaries, regional flows, and inflows from surface streams and accumulations are common in karst areas. Due to the lack of reliable methods for determination of water balance in the phreatic zone of such aquifers, groundwater recharge estimation is a challenge task. This paper introduces a new method for estimation of groundwater recharge in karst – the so-called partial correlation method (PCM). The basic hypothesis is that the groundwater recharge rates can be determined from the time series of precipitation, air temperature, relative humidity, and spring discharge, by using a partial cross-correlation function as objective function. Following this hypothesis, a simple conceptual model of water balance in the soil cover, epikarst and vadose zone is developed, and an objective function for estimation of the optimal value of parameter of this model is proposed. PCM is applied on the catchment of Žrnovnica Spring located in the Dinaric karst area of Croatia. The results of application are compared with the results of previous studies, as well as with the results obtained by five empirical models that have been used for estimation of groundwater recharge in the Mediterranean karst. The effective infiltration coefficients obtained by PCM for the Žrnovnica Spring are generally in accordance with the previously published ones.

Assessment of Soil Erosion by RUSLE Model using Remote Sensing and GIS of Indla-Ghatkhed, District-Amravati, Maharashtra

The catchment boundary of Indla Ghatkhed watershed covers an area about 14..62 sq km. The erosion is a natural geomorphic process occurring continually over the earth’s surface and it largely depends on topography, vegetation, soil and climatic variables and, therefore, exhibits pronounced spatial variability due to catchments heterogeneity and climatic variation. This problem can be circumvented by discrediting the catchments into approximately homogeneous sub-areas using Geographic Information System (GIS). Soil erosion assessment modeling was carried out based on the Revised Universal Soil Loss Equation (RUSLE). A set of factors are involved in RUSLE equation are A = Average annual soil loss (mt/ha/year), R = Rainfall erosivity factor (mt/ha/year), k = Soil erodibility factor, LS = Slope length factor, C = Crop cover management factor, P = Supporting conservation practice factor. These factors extracted from different surface features by analysis and brought in to raster format. The output depicts the amount of sediment rate from a particular grid in spatial domain and the pixel value of the outlet grid indicates the sediment yield at the outlet of the watershed.

Characteristic Scales of Drainage Reorganization in Cascadia

AbstractVariations in uplift, erosion, climate, and bedrock are commonly invoked as key controls on drainage basin morphology, yet the scale of landforms that define changes in regional drainage networks has not been addressed, limiting our ability to predict their planform evolution. Here we use two‐dimensional (2D) continuous wavelet transforms of topography in Cascadia to highlight dominant topographic features at different scales. Surprisingly, our wavelet analysis shows that for wavelengths >30 km, the Cascadia Forearc Lowland (CFL) spans the entire margin. Separately, we compare observed catchment boundaries with synthetic boundaries generated on topography filtered with 2D Gaussian functions. We observe reorganization of synthetic drainage networks from an arc‐to‐coast drainage system into arc‐spanning, margin‐parallel river systems, akin to the modern Willamette River and coincident with the CFL. In concert with field observations of stream capture and Willamette Valley expansion, we propose that the Cascadia forearc is actively transitioning to a predominately margin‐parallel river system.

Where do low risk women live relative to maternity services across Victoria? Expanding access to public homebirth models across Victoria

ProblemCurrently <1% of Australian women give birth at home. BackgroundIn Australia there are very few options for women to access public funded homebirth. AimWe aimed to use geo-mapping to identify the number of women eligible for homebirth in Victoria, based on the criteria of uncomplicated pregnancies and residing within 15–25kms of suitable maternity services, to plan future maternity care options. MethodsRetrospective study of births between 2015 and 2017 in Victoria, Australia. All women who were identified as having a low risk pregnancy at the beginning of pregnancy were included. The number of women within 15 and 25km of a suitable Victorian public maternity hospital and catchment boundaries around each hospital were determined. FindingsBetween 2015 and 2017, 126,830 low risk women gave birth in Victoria, of whom half live within 25km of seven Victorian hospitals. Currently, 2% of suitable women who live close to the current public homebirth models accessed them. DiscussionWe present a method to inform the expansion of maternity service options using Victoria as an example. On the basis of the maximum number of low risk women living close by, we have also identified the Victorian maternity services that would be most suitable for creation of public homebirth or low risk continuity of midwifery models. ConclusionThis approach could can be used to plan other maternity care services.

The development process of the Korean coastal mountain range: Examination from spatial distribution of knickzones

Along the eastern margin of the Korean Peninsula, a coastal mountain range spanning over 800 km with summits above 1500 m faces the East Sea (or Sea of Japan), the back-arc sea behind the Japanese Islands. Two contrasting hypotheses exist regarding the tectonic history of this coastal mountain range: long-lasting and progressive uplifts from the Early Tertiary to the Late Quaternary, and a short and intensive uplift during the Early Miocene. However, to date, no consensus has been reached. Here, we studied the spatial distribution of knickzones to understand the formation period and development pattern of this coastal mountain range. We extracted the knickzones in a drainage basin from digital elevation models, and investigated whether or not they are transient knickzones induced by the development of the coastal mountain range. We found that all identified knickzones were stationary, which was verified by slope-area and chi-elevation analyses. This implies that sufficient time has passed for all transient knickzones relevant to the growth of the mountain range to migrate up to the catchment boundary and disappear. We then calculated the time spent for the migration of transient knickzones from the outlet to their stream heads to be at least 5.1 to 10.6 Myr. Therefore, our results suggest that the current form of the coastal mountain range had been built at least before 5.1 Myr ago and has reached a quasi-equilibrium state up to the present, thus invalidating the prevailing hypothesis of the long-lasting and progressive development until the Late Quaternary.

Inventory and Connectivity Assessment of Wetlands in Northern Landscapes with a Depression-Based DEM Method

Wetlands, including peatlands, supply crucial ecosystem services such as water purification, carbon sequestration and regulation of hydrological and biogeochemical cycles. Peatlands are especially important as carbon sinks and stores because of the incomplete decomposition of vegetation within the peat. Good knowledge of individual wetlands exists locally, but information on how different wetland systems interact with their surroundings is lacking. In this study, the ability to use a depression-based digital elevation model (DEM) method to inventory wetlands in northern landscapes and assess their hydrological connectivity was investigated. The method consisted of three steps: (1) identification and mapping of wetlands, (2) identification of threshold values of minimum wetland size and depth, and (3) delineation of a defined coherent area of multiple wetlands with hydrological connectivity, called wetlandscape. The results showed that 64% of identified wetlands corresponded with an existing wetland map in the study area, but only 10% of the wetlands in the existing map were identified, with the F1 score being 17%. Therefore, the methodology cannot independently map wetlands and future research should be conducted in which additional data sources and mapping techniques are integrated. However, wetland connectivity could be mapped with the depression-based DEM methodology by utilising information on upstream and downstream wetland depressions, catchment boundaries and drainage flow paths. Knowledge about wetland connectivity is crucial for understanding how physical, biological and chemical materials are transported and distributed in the landscape, and thus also for resilience, management and protection of wetlandscapes.

Regional features of topographic relief over the Loess Plateau, China: evidence from ensemble empirical mode decomposition

Landforms with similar surface matter compositions, endogenic and exogenic forces, and development histories tend to exhibit significant degrees of self-similarity in morphology and spatial variation. In loess hill-gully areas, ridges and hills have similar topographic relief characteristics and present nearly periodic variations of similar repeating structures at certain spatial scales, which is termed the topographic relief period (TRP). This is a relatively new concept, which is different from the degree of relief, and describes the fluctuations of the terrain from both horizontal and vertical (cross-section) perspectives, which can be used for in-depth analysis of 2-D topographic relief features. This technique provides a new perspective for understanding the macro characteristics and differentiation patterns of loess landforms. We investigate TRP variation features of different landforms on the Loess Plateau, China, by extracting catchment boundary profiles (CBPs) from 5 m resolution digital elevation model (DEM) data. These profiles were subjected to temporal-frequency analysis using the ensemble empirical mode decomposition (EEMD) method. The results showed that loess landforms are characterized by significant regional topographic relief; the CBP of 14 sample areas exhibited an overall pattern of decreasing TRPs and increasing topographic relief spatial frequencies from south to north. According to the TRPs and topographic relief characteristics, the topographic relief of the Loess Plateau was divided into four types that have obvious regional differences. The findings of this study enrich the theories and methods for digital terrain data analysis of the Loess Plateau. Future study should undertake a more in-depth investigation regarding the complexity of the region and to address the limitations of the EEMD method.

Impact of Forest Cover Change on Available Water Resources: Long-Term Forest Cover Dynamics of the Semi-Arid Dhofar Cloud Forest, Oman

Forest cover dynamics are an important indicator for climate change as well as for land conversion studies. Based on an analysis of 30 years of Landsat data a forest cover time series was generated and analyzed for the Dhofar mountains in Oman. The Dhofar mountains in Southern Oman with its semi-arid cloud forest is an important asset for livestock, water resources, and tourism. In this study we investigated whether forest cover trends are distinguishable and what impact forest cover changes have on water availability. To cope with gaps in the Landsat dataset the Dhofar mountains were divided into regions of interest (ROIs) that were based on hydrologic catchment boundaries. The results show, that, despite increasing pressure from tourism and increasing livestock numbers, the forest cover shows slight but not significant increases in most ROIs and significant forest cover increases in three ROIs. Overall, forest cover during the past 30 years is at least stable and most probably slightly increasing. With regard to water resources results show that, the impact of cloud forest interception amounts to an additional subcanopy water input of about 15 to 150 % of annual rainfall. This additional water is only available below tree cover. Part of that water is, of course used by plant transpiration, however, the stemflow portion which is exceptionally high in this region infiltrates directly into deeper soil layers and eventually leads to groundwater recharge.

Watershed Delineation of Rivers in Karaikal District using Remote Sensing and GIS Technique

Water carry nutrients to areas all around the earth. They play a most important part in the water cycle, acting as drainage channels for surface water. Rivers provide good habitat and food for many of the earth's organisms. The purpose of this study is to delineate the watersheds basin in the Karaikal district from Bhuvan and United States Geological Survey (USGS) website. Digital Elevation Model is the main data source for extracting hydrology data in ArcGIS. Model Builder was the key for creation of Flow Accumulation, Stream segment, pour point and contour has been prepared using surface tool in ArcGIS software. Watershed delineation map is obtained by integration of Flow Accumulation, Stream segment and Pour point. Watershed analysis provides catchment boundaries but also hydrological parameters useful for management programs.

The Issues of Catchment Boundaries Delimitation in a Suburban Area – the Case Study of Poznań Metropolitan Area, Poland

The Issues of Catchment Boundaries Delimitation in a Suburban Area – the Case Study of Poznań Metropolitan Area, Poland

Assessing the influence of DEM source on derived streamline and catchment boundary accuracy

Accurate DEM-derived streamlines and catchment boundaries are essential for hydrological modelling. Due to the popularity of hydrological parameters derived mainly from free DEMs, it is essential to investigate the accuracy of these parameters. This study compared the spatial accuracy of streamlines and catchment boundaries derived from available digital elevation models in South Africa. Two versions of Stellenbosch University DEMs (SUDEM5 and DEMSA2), the second version of the 30 m advanced spaceborne thermal emission and reflection radiometer global digital elevation model (ASTER GDEM2), the 30 and 90 m shuttle radar topography mission (SRTM30 and SRTM90 DEM), and the 90 m Water Research Commission DEM (WRC DEM) were considered. As a reference, a 1 m GEOEYE DEM was generated from GeoEye stereo images. Catchment boundaries and streamlines were extracted from the DEMs using the Arc Hydro module. A reference catchment boundary was generated from the GEOEYE DEM and verified during field visits. Reference streamlines were digitised at a scale of 1:10 000 from the 1 m orthorectified GeoEye images. Visual inspection, as well as quantitative measures such as correctness index, mean absolute error, root mean squares error and figure of merit index were used to validate the results. The study affirmed that high resolution (&lt;30 m) DEMs produce more accurate parameters and that DEM source and resampling techniques also play a role. However, if high resolution DEMs are not available, the 30 m SRTM DEM is recommended as its vertical accuracy was relatively high and the quality of the streamlines and catchment boundary was good. In addition, it was found that the novel Euclidean distance-based MAE and RMSE proposed in this study to compare reference and DEM-extracted raster datasets of different resolutions is a more reliable indicator of geometrical accuracy than the correctness and figure of merit indices.