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The quantitative analysis of drainage system is an important aspect of characterization of watersheds. Using watershed as a basin unit in morphometric analysis is the most logical choice because all hydrological and geomorphic processes occur within the watershed. The Budigere Amanikere watershed a tributary of Dakshina Pinakini River has been selected for case illustration. Geoinformatics module consisting of ArcGIS 10.3v and Cartosat-1 Digital Elevation Model (DEM) version 1 of resolution 1 arc Sec (~32 m) data obtained from Bhuvan is effectively used. Sheet and gully erosion are identified in parts of the study area. Slope in the watershed indicating moderate to least runoff and negligible soil loss condition. Third and fourth-order sub-watershed analysis is carried out. Mean bifurcation ratio ( R b ) 3.6 specify there is no dominant influence of geology and structures, low drainage density ( D d ) 1.12 and low stream frequency ( F s ) 1.17 implies highly infiltration subsoil material and low runoff, infiltration number ( I f )1.3 implies higher infiltration capacity, coarse drainage texture ( T ) 3.40 shows high permeable subsoil, length of overland flow ( L g ) 0.45 indicates under very less structural disturbances, less runoff conditions, constant of channel maintenance ( C ) 0.9 indicates higher permeability of subsoil, elongation ratio ( R e ) 0.58, circularity ratio ( R c ) 0.75 and form factor ( R f ) 0.26 signifies sub-circular to more elongated basin with high infiltration with low runoff. It was observed from the hypsometric curves and hypsometric integral values of the watershed along with their sub basins that the drainage system is attaining a mature stage of geomorphic development. Additionally, Hypsometric curve and hypsometric integral value proves that the infiltration capacity is high as well as runoff is low in the watershed. Thus, these mormometric analyses can be used as an estimator of erosion status of watersheds leading to prioritization for taking up soil and water conservation measures.

Lake volume variation is closely related to climate change and human activities, which can be monitored by multi-source remote-sensing data from space. Although there are usually two routine ways to construct the lake volume by the digital elevation model (DEM) or satellite altimetric data combined with the lake area, rarely has a comparison been made between the two methods. Therefore, we conducted a comparison between the two methods in Texas for 14 lakes with abundant validation data. First, we constructed the lake hypsometric curve by five commonly applied DEMs (SRTM, ASTER, ALOS, GMTED2010, and NED) or satellite altimetric products combined with the gauge lake area. Second, the lake volume was estimated by combining the hypsometric curve with the gauge lake area time series. Finally, the estimation error has been quantitatively calculated. The results show that the relative lake volume estimation error (rVSD) of the altimetric data (4%) is only 10–18% of that of the DEMs (22–41%), and the DEM with the highest resolution (NED) has the least rVSD with an average of 22%. Therefore, for large-scale lake monitoring, we suggest the application of satellite altimetric data with the lake area to estimate the lake volume of large lakes, and the application of high-resolution DEM with the lake area to calculate the lake volume of small lakes that are gapped by satellite altimetric data.

Coastal intertidal soft-sediment habitats provide ecosystem services to millions of people worldwide, yet are under intense pressure from land-use change and sea-level rise (SLR). Both pressures interact to reduce light reaching the seafloor, thereby disrupting benthic primary producers and the ecosystem functions and services they provide. This study considers the implications of altered light climate on microphytobenthic (MPB) production in shallow estuaries. Continuous measurements of seafloor photosynthetically active radiation (PAR) were made over 9 mo on intertidal sandflats in 14 New Zealand estuaries spanning a turbidity gradient. A literature summary of benthic photosynthesis−irradiance curves was used to predict PAR limitation at sampling sites. Estimates of the proportion of time MPB would be light limited during emersion ranged from a median of 32−64% compared to a median of 55−100% during immersion. For estuaries close to 100% PAR limitation during immersion, emerged intertidal areas represent a refuge for MPB production which is vulnerable to SLR. Based on hypsometric curves (a representation of estuary bathymetry), the intertidal area of our study estuaries is predicted to decrease by 27−94% in response to SLR of 1.4 m. The combination of high PAR limitation during immersion and large losses of intertidal area will increase vulnerability to the loss of MPB production and the associated ecosystem services, which will push these ecosystems towards tipping points. The research highlights how the interplay between local and global scale stressors may ultimately trigger ecological collapse under future global change.

Lakes provide important water resources and many essential ecosystem services. Some of Earth's largest lakes recently reached record‐low levels, suggesting increasing threats from climate change and anthropogenic activities. Yet, continuous monitoring of lake levels is challenging at a global scale due to the sparse in situ gauging network and the limited spatial or temporal coverage of satellite altimeters. A few pioneering studies used water areas and hypsometric curves to reconstruct water levels but suffered from large uncertainties due to the lack of high‐quality hypsometry data. Here, we propose a novel proxy‐based method to reconstruct multi‐decadal water levels from 1992 to 2018 for both large and small lakes using Landsat images and ICESat (2003–2009) and recently launched ICESat‐2 (2018+) laser altimeters. Using the new method, we evaluate reconstructed levels of 342 lakes worldwide, with sizes ranging from 1 to 81,844 km2. Reconstructed water levels have a median root‐mean‐square error (RMSE) of 0.66 m, equivalent to 57% of the standard deviation of monthly level variability. Compared with two recently reconstructed water level data sets, the proposed method reduces the median RMSE by 27%–32%. The improvement is attributable to the new method's robust construction of high‐quality hypsometry, with a median R2 value of 0.92. Most reconstructed water level time series have a bi‐monthly or higher frequency. Given that ICESat‐2 and Landsat can observe hundreds of thousands of water bodies, this method can be applied to conduct an improved global inventory of time‐varying lake levels and thus inform water resource management more broadly than existing methods. Key Points Landsat images and laser altimeters were leveraged to reconstruct multi‐decadal lake levels of both large and small lakes Reconstructed water levels were validated against observed levels on 342 global lakes with a median error of 0.66 m Most of the reconstructed lake level time series have a bi‐monthly or higher frequency

The existing literature discussed only the aerial aspect and provided a brief description of tectonic-geomorphic correlation with field evidence. In present study we applied power law equations to estimate basin asymmetry factor (AF), Transverse topographic asymmetric factor (T), Hypsometric Integral (HI), longitudinal profile, stream length gradient index (SL), steepness index (Ksn), Chi (χ) and knick point (Kp) analysis to examine the response of tectono-climatic fluctuations in the Mandakini River basin, central Uttarakhand Himalaya. To decouple the causative tectono-climatic factors, we employed geospatial and Stream Power Incision Modeling (SPIM) techniques. SPIM is a globally accepted tool to predict an equilibrium state between fluvial erosion rates and the escalating function of stream power. It is actively applied in modeling the transformation of river systems especially in rugged topographic regions. The present study covers SPIM-based morphometric assessment of the tectonically sensitive Mandakini River basin between Ramgarh Thrust (RT) and Vaikrita Thrust (VT) in the central region of Uttarakhand Himalaya. In the upper reaches of the basin, U-shaped glaciated valleys dominate the landscape, while a rolling topography and deeply incised narrow valleys are depicted towards the downstream. Therefore, to understand the response of active tectonic over geomorphology, the drainage basin has been divided into two separate zones from the confluence point near the Rampur area. The modeling outcomes indicate that the Mandakini drainage basin is in a disequilibrium state where channels are actively incising to bedrock. Overall, AF of 32 and 70 indicate leftward tilting in the upper reaches and rightward tilting in the lower reaches of the basin, respectively. The HI value of 0.38 indicates a stage of maturity, characterized by a concave shape profile. Based on the analysis it may be concluded that the fragile lithology and tectono-climatic fluctuations are dominantly controlling the topography and valley floor morphology of the Mandakini River.

The Mountain Front Flexure marks a dominant topographic step in the frontal part of the Zagros Fold–Thrust Belt. It is characterized by numerous active anticlines atop of a basement fault. So far, little is known about the relative activity of the anticlines, about their evolution, or about how crustal deformation migrates over time. We assessed the relative landscape maturity of three along-strike anticlines (from SE to NW: Harir, Perat, and Akre) located on the hanging wall of the Mountain Front Flexure in the Kurdistan Region of Iraq to identify the most active structures and to gain insights into the evolution of the fold–thrust belt. Landscape maturity was evaluated using geomorphic indices such as hypsometric curves, hypsometric integral, surface roughness, and surface index. Subsequently, numerical landscape evolution models were run to estimate the relative time difference between the onset of growth of the anticlines, using the present-day topography of the Harir Anticline as a base model. A stream power equation was used to introduce fluvial erosion, and a hillslope diffusion equation was applied to account for colluvial sediment transport. For different time steps of model evolution, we calculated the geomorphic indices generated from the base model. While Akre Anticline shows deeply incised valleys and advanced erosion, Harir and Perat anticlines have relatively smoother surfaces and are supposedly younger than the Akre Anticline. The landscape maturity level decreases from NW to SE. A comparison of the geomorphic indices of the model output to those of the present-day topography of Perat and Akre anticlines revealed that it would take the Harir Anticline about 80–100 and 160–200 kyr to reach the maturity level of the Perat and Akre anticlines, respectively, assuming erosion under constant conditions and constant rock uplift rates along the three anticlines. Since the factors controlling geomorphology (lithology, structural setting, and climate) are similar for all three anticlines, and under the assumption of constant growth and erosion conditions, we infer that uplift of the Akre Anticline started 160–200 kyr before that of the Harir Anticline, with the Perat Anticline showing an intermediate age. A NW-ward propagation of the Harir Anticline itself implies that the uplift has been independent within different segments. Our method of estimating the relative age difference can be applied to many other anticlines in the Mountain Front Flexure region to construct a model of temporal evolution of this belt.

Understanding the causes and consequences of forest-fragmentation changes is critical for preserving various ecosystem services and to maintain biodiversity levels. We used long-term (1860s–2010s) and large-scale data on historical forest cover in the Polish Carpathians to identify the trajectories of forest fragmentation. Past forest cover was reconstructed for the 1860s, 1930s, 1970s and 2010s using historical maps and the contemporary national database of topographic objects. We analyzed forest-cover changes in 127 randomly selected circular test areas. Forest fragmentation was quantified with GuidosToolbox software using measures based on a landscape hypsometric curve (LHC). Despite a general increase in forest cover, forest fragmentation showed divergent trajectories: a decrease between the 1860s and 1930s (in 57% of test areas), and an increase between the 1930s and 1970s and between the 1970s and 2010s (in 58% and 72% of test areas, respectively). Although deforestation typically involves the increasing fragmentation of forest habitats, we found that forest expansion may not necessarily lead to more homogenous forested landscape, due to complex land-ownership and land-use legacy patterns. This is both a challenge and an opportunity for policy makers to tune policies in such a way as to maintain the desired fragmentation of forest habitats.

The division and evaluation of data series used in monitoring drought into different time intervals is a practical approach to detecting the spatial and temporal extent of drought spread. This study aimed to determine meteorological drought’s spatial and temporal distribution using overlapping and consecutive periods and cycles of the standardized precipitation index (SPI) time series in the Mediterranean region, Turkey. In the scope of the research, SPI values for the SPI12, SPI6 (1), and SPI6 (2) seasons were calculated for consecutive and overlapping hydrological years (1978–1998/21 years, 1978–2008/31 years, and 1978–2018/41 years) at 28 meteorological stations. Autocorrelation, Mann–Kendall, and Sen slope trend tests were applied at a 5% significance level for each season (SPI12, SPI6 (1), and SPI6 (2)) and different time scales (21, 31, and 41 years). For each season and period, maps of the SPI drought class, average formation of drought class, Mann–Kendall (MK) trend, and Sen’s slope (SS) trend test statistics for the Mediterranean region were obtained, and the spatial distribution rate of trends was determined by drawing hypsometric curves. Changes in drought occurrence at different time scales were thoroughly evaluated with the changing length of data recording. Consequently, it was determined that the mild wet (MIW) and mild drought (MID) classes dominate the study area in the Mediterranean region. Significant and nonstationary changes detected in extreme wet and drought occurrences (extreme wet, EW; severe wet, SW; extreme drought, ED; severe drought, SD) were found to pose a risk in the study area. It was observed that there were spatially and temporally insignificant decreasing drought trends in the Mediterranean basin, considering that the time scales of these trends slowed down. Despite a nonsignificant trend from the MID drought class to the MIW drought class, it is predicted that the MIW and MID classes will maintain their dominance in the Mediterranean region. The central part of the study area (central Mediterranean basin) is the region with the highest drought risk.

Methods for soil water conditions assessment are often highly localized or data demanding. In this study we propose a new scalable approach to assess soil water conditions. The main goal is to test whether the approach can be used to provide information about local conditions, without the need of extensive data sets. The approach utilizes a combination of normalized topography derived from the HAND terrain model (Height Above the Nearest Drainage) and hypsometric curves to identify wet and saturated areas for any given geographical extent. The study was conducted through a case study in the Lagan River catchment in the southwest of Sweden. To analyze the performance of the approach, a non‐linear regression analysis was performed to assess the relationship between the fraction of wet area and the normalized terrain. This was followed by a correlation analysis, in which the correspondence of the derived output was validated against the national Soil Moisture Map provided by the Swedish University of Agricultural Sciences. The results show a strong, and statistically significant, negative exponential relationship between the fraction of wet area, and the maximum heights within the studied area. The approach also corresponds well with the spatial variations highlighted in the Soil Moisture Map, although better in predicted wetter areas than under dry conditions. Going forward, we believe the integration of hypsometric curves and the HAND model could not only improve water balance calculations but assist in the assessments of flood and drought‐prone areas. Key Points Hypsometric curves in combination with normalized terrain data can be used to assess soil moisture with limited data requirements The inclusion of flexible and scalable parameters facilitates local adaptation and allow a broad application of the proposed approach The proposed approach could prove useful for water balance calculations, flood management and agriculture

The formation and evolution of management gullies is a highly intense process of soil erosion often overlooked in policies and river basin strategies. Despite the worldwide spread of the phenomenon, our ability to assess and simulate gullying and its impacts remains limited; therefore, predicting the development and evolution of these river reaches represents a significant challenge, especially in areas where the loss of productive soil or the hazards linked to landslides or floods represent critical factors. Our study demonstrates how an exclusively morphometric approach, based on the construction of the hypsometric curve and applied to small hydrographic basins that are lithologically homogeneous and hierarchized according to the Strahler classification method, is able to predict the triggering height of the gullies; this height corresponds to the mean elevation of the basin and the inflection point of the hypsometric curve itself, confirming the hypothesis that this point coincides with the point at which a sudden change in surface runoff energy occurs, The study also shows that the portion of the basin necessary to trigger these intense erosive processes is always within a small range, regardless of the size and morphology (slope) of the basin itself. Such an approach, which is quick and relatively easy to apply, could help develop hydrogeological hazard mitigation practices in land planning projects.