Watershed Land Use Research Articles

Response of Macrophyte Diversity in Coastal Lakes to Watershed Land Use and Salinity Gradient.

Coastal lakes are subject to multiple stressors, among which land use, hydrological connectivity, and salinity have the greatest effect on their biodiversity. We studied the effects that various land cover types (CORINE) of coastal lake watersheds had on macrophyte diversity in ten coastal lakes along the southern Baltic coast as characterised by twelve phytocenotic indices: these being a number of communities, Shannon-Wiener diversity, evenness, and indices of taxonomic distinctiveness of plant communities: vegetation coverage; colonisation index; share of the phytolittoral area in the total lake area, as well as shares of nympheides, pondweeds, charophytes, marine, emerged and submerged communities in the total lake area. The effects were checked for three groups of lakes distinguished by differences in salinity-freshwater (F, 5), transitional (T, 4), and brackish (B, 1)-in which a total of 48 macrophyte communities were identified. The most abundant in aquatic phytocoenoses were lakes of T type. A partial least squares regression model (PLS-R) showed a stronger impact of land-use types in immediate vicinities and entire watersheds than the impact of physico-chemical properties of water on phytocenotic indices in the lakes. Macrophyte diversity was relatively low in urban and agricultural catchments and relatively high in forest and wetland areas. Agriculture had a negative impact on the number of macrophyte communities in F lakes and, in T lakes, on the number of macrophyte communities, biodiversity, evenness, and proportion of emerged, submerged, and marine communities. Urban areas contributed to lower values of evenness, vegetation coverage, and share of marine communities in F, but, in T, to lower the number of macrophyte communities, evenness, and proportion of submerged and marine communities. Our results confirm the significant impact of land use on macrophyte diversity in coastal aquatic ecosystems. Combined analysis of anthropogenic and natural descriptors is a prerequisite for analysing human threats to biodiversity in coastal lakes. Macrophyte community-based measures of biodiversity are sensitive indicators of anthropogenic impact on the ecological condition of coastal ecosystems.

Spatiotemporal Dynamic Characteristics of Land Use in the Typical Watershed of Wenchuan Earthquake-Affected Areas—A Case Study in the Longxi River Basin

Major earthquakes cause serious damage to ecosystem structure and function through their huge destructive force and subsequent geohazards. Understanding the characteristics of post-earthquake land use change is of great interest to assess the effects of ecological restoration in earthquake-affected areas. However, little is known about the consequences of land use change on a small scale due to incomplete, non-comprehensive, and sparse research data. Here, we used remote-sensing images to study the land use change characteristics of the Longxi River before and after the Wenchuan earthquake by calculating the land use dynamics degree, transition matrix, and gravity center of the Longxi River Basin from 2005 to 2015. The Wenchuan earthquake disaster did not affect the main dominance of forests. Grassland, the second dominant land type, was replaced by geohazard-induced unutilized land after the earthquake. Compared with pre-earthquake in 2005, the areas of cultivated land, forest, grassland, and water area decreased, while those of construction land and unutilized land increased in 2015. The single land use dynamic degree and spatial dynamic change degree show the highest transition intensity of other land use types to unutilized land between 2005 and 2009. However, the degrees of all land use types decreased between 2009 and 2015. Both banks of the lower reach of the Longxi River had high and developing comprehensive indexes of land use degrees during the study period. The gravity centers of grassland, construction land, water, and cultivated land changed from north to south, while forest and unutilized land had the opposite pattern. Our results provide useful information for ecological restoration, ecological security, and soil-erosion control in earthquake-affected areas.

Hydrological connectivity affects nitrogen migration and retention in the land‒river continuum

Land use change and excessive nitrogen (N) loading threaten the health of receiving water bodies worldwide. However, the role of hydrological connectivity in linking watershed land use, N biogeochemistry and river water quality remain unclear. In this study, we investigated 15 subwatersheds in the Jiulong River watershed (southeastern China) during a dry baseflow period in 2018, combined with 3‒year (2017–2019) nutrient monitoring in 5 subwatersheds to explore river N dynamics (dissolved nutrients, dissolved gases and functional genes) and their controlling factors at three hydrological connectivity scales, i.e., watershed, hydrologically sensitive areas (HSAs) and riparian zone. The results show that land use at HSAs (less than 20% of watershed area) and watershed scales contributed similarly to river N variation, indicating that HSAs are hotspots for transporting land N into river channels. In particular, the agricultural land was the main factor affecting river nitrate and nitrous oxide (N2O) concentrations, while the built–up land significantly affected river ammonium and nitrite. At the riparian zone scale, soils and sediments substantially influenced river N retention processes (i.e., nitrification and denitrification). Management and protection measures targeting HSAs and riparian zones are expected to efficiently reduce river N loading and improve water quality.

Efforts to Reduce River Water Discharge through Land Use Control (Case Study: Upstream Ciliwung Watershed, Indonesia)

Land-use change is the main cause of high runoff compared to other factors. The type of land use also plays a role in determining the amount of runoff that occurs. The Upstream Ciliwung watershed is blamed as the main causes of the flood disaster in Jakarta, the capital city. The land use in the upper stream has changed and causes increasing of run off to be higher than the capacity of river to drain it. This study aims to explore the land use changes of the Upstream Ciliwung Watershed from 1996 to 2016 and their consequences on the stream run off. Furthermore, the study also recommends the efforts needed to reduce river water discharge. The land use changes are identified by using spatial analysis method. The calculation of run off uses the rational method. Average rainfall data for every ten years is calculated by use of Gumbell distribution formula. The study shows that in the period 1996 – 2016, there was a change in land use in the upstream Ciliwung watershed. The area that continues to decline includes primary forest, open land, paddy fields, shrubs, and mixed gardens, all of which are categorized as undeveloped areas. The runoff discharge from 1996 – 2016 has increased from 278.77 to 465.57 mm/second that indicate runoff discharge is already in the Standby I position. Efforts that need to be made to reduce runoff water flow in the Ciliwung watershed are: 1) consistently develop and control land use change in the area based on the Jabodetabekpunjur Spatial Planning 2) consistently apply the building coverage ratio (BCR) regulation; 3) construct engineering and technology approach such as build infiltration wells in settlement, 4) forest rehabilitation and 5) conducting law enforcement.

Site Suitability Analysis for Surface Irrigation using GIS, Remote Sensing, and Analytical Hierarchy Process (AHP) Integration in Wama Watershed, Western Ethiopia

The study integrates GIS, Remote Sensing and Analytical Hierarchy Process (AHP) to evaluate suitable sites for surface irrigation by taking eight parameters into account, including slope, elevation, distance to water source, land use, soil texture, soil type, soil depth, and soil drainage in Wama watershed. A numeric range was created by standardizing each parameter to a single measurement scale, with higher values denoting more suitable and lower values denoting less suitable one. The final site suitability map was prepared in GIS environment by using the weighted overlay method. Distance to streams (44%), slope (18%), elevation (13%), LULC (13%), and soil drainage (5%) scored highly in the pairwise comparison matrix. Additionally, they are the most crucial elements in evaluating eligible lands for surface irrigation, followed by soil depth (4%), soil type (3%), and soil texture (2%). The final suitability map, which will aid in supporting rain-fed agriculture by surface irrigation, was developed with four classifications highly suitable (16%), moderately suitable (49%), marginally suitable (34%), and not suitable (1%). Therefore, this study demonstrates a robust method of using GIS and remote sensing techniques, which is efficient and useful in mapping potential site suitability for surface irrigation and an important guideline for planners, and decision-makers to give the fast decision for irrigation management.

Microhabitat and Landscape Drivers of Richness and Abundance of Freshwater Mussels (Unionida: Unionidae) in a Coastal Plain River

Although rivers support significant unionid mussel (Unionida: Unionidae) diversity, Gulf of Mexico tributary rivers have been subject to changes in water quality and habitat due to altered watershed land use. We quantified mussel species richness and relative abundance and environmental factors in small tributary streams of the Pearl River, Mississippi-Louisiana. Freshwater mussel and habitat surveys were conducted at 27 stream sampling sites over two summers (9 sites revisited), and coverage of seven land use categories and seven geological categories above each reach were calculated. Mussels were patchily distributed (53% of sites sampled yielded mussels) and typically not abundant (only 26% of sites yielded >10 mussels). Surveys revealed nine species, with total abundance ranging from 0–66 mussels and richness ranging from 0–5 species per site. Assemblages were driven by an upper to lower watershed gradient of decreasing CPUE and richness, with microhabitat and water quality, land cover, and geology locally modifying this gradient. Environmental variables did not seem of sufficient magnitude to account for the patchy distributions and low abundances of mussels at most study sites, and we hypothesize that high discharge events related to tropical storm passage may have exerted an overriding influence on mussel assemblages in these streams through direct mortality and/or altered availability of suitable glochidial hosts.

Effects of watershed land use on coastal marine environments: A multiscale exploratory analysis with multiple biogeochemical indicators in fringing coral reefs of Okinawa Island.

The analytical spatial scale and selection of biogeochemical indicators affect interpretations of land-use impacts on coastal marine environments. In this study, nine biogeochemical indicators were sampled from 36 locations of coral reefs fringing a subtropical island, and their relationships with watershed land use were assessed by spatial autoregressive models with spatial weight matrixes based on distance thresholds of a few to 30km. POM-relevant indicators were associated with agricultural and urban lands of watersheds within relatively small ranges (6-14km), while the concentrations of inorganic nutrients were associated with watersheds within 20km or more. The macroalgal δ15N showed a strong relationship with agricultural lands of watersheds within 7km and urban/forest lands of watersheds within 24km. These results demonstrate significant effects of land use on the coral reef ecosystems of the island, and the importance of appropriate combinations of analytical scales and biogeochemical indicators.

Environmental analysis of land use and occupation in nine watersheds contributing to the Iguaçu River, Brazil

The land use and occupation in watersheds directly influences the water resources, and the vegetation cover is a crucial factor for water maintenance. The objective of this study was to characterize the land use and occupation in nine watersheds of the Lower Iguaçu River (Andrada, Monteiro, Gonçalves Dias, Floriano, Silva Jardim, Cotejipe, Sarandi, Capanema and Santo Antônio sub-basin rivers), using the classification from satellite images. The classification area obtained high accuracy (Kappa coefficient of 99.4 to 99.9%). The Floriano River sub-basin presented the highest degree of environmental preservation, followed by Silva Jardim and Gonçalves Dias River sub-basins, fully or partially inserted in Iguaçu National Park. Monteiro and Sarandi river sub-basins showed the smallest areas of vegetation, and Capanema, Cotejipe, Andrada and Santo Antônio River sub-basins exhibited an intermediate condition. This tendency was verified by the cluster analysis. These results can serve as a baseline for planning, monitoring and management of this area, environmental modeling, conservation of water resources, biodiversity, and environmental services.

Riparian and watershed land use alters food web structure and shifts basal energy in agricultural streams

Riparian and watershed land use alters food web structure and shifts basal energy in agricultural streams

Exploring the Impact of Landscape Ecological Risk on Water Quality in the Danjiangkou Reservoir, China

AbstractEvaluating the spatial‐temporal dynamics in ecological risk and understanding its impact on water quality in reservoirs could optimize watershed land use and protect reservoir water quality. However, this impact remains elusive due to the lack of long‐term field data, the heterogeneity of land use, and scale effects. Therefore, Danjiangkou Reservoir area was selected as the study area, where rapid urban expansion and ecological conservation and restoration measures have significantly changed the ecological environment, altering the water quality. We investigated the spatial‐temporal changes of land use from 1990 to 2020 and evaluated how landscape ecological risk changed, as well as explored the impact of landscape ecological risk changes on water quality. The landscape ecological risk was calculated by landscape vulnerability and landscape disturbance (based on fragmentation, separation, and fractal dimension). The results indicated that the growth rate of water bodies surged (7.65 km2/a) and cropland experienced an apparent reduction (14.39%) over the past 30 years. These landscape changes decreased ecological risk, especially after the water transfer. The results revealed that the impacts of ecological risk on water quality were better explained at the riparian scale than at the reach and catchment scales. Specifically, the ecological risk was strongly relevant to dissolved oxygen, Turbidity, Cl− and , and moderately correlated to Ca2+ and pH. While it was not correlated with total nitrogen, total phosphorus, and F−, possibly due to the irregular reservoir operations, occasional excessive use of fertilizers, and rock weathering. This study preliminarily discloses the impact of landscape ecological risk on water quality in a basin reservoir and provides a theoretical basis to take measures in advance for the sustainable development of a reservoir basin.

Zooplankton assemblage structure and diversity since pre‐industrial times in relation to land use

AbstractAimWhile it is now well accepted that human activities are having pronounced effects on natural ecosystems, regional variation in the rate and magnitude of various human impacts is unclear. Moreover, the effects of land use change on natural aquatic communities have only relatively recently begun to be explored. Our goal was to understand how and where assemblages of a central food web component of freshwater lakes have changed over the course of industrialization in relation to land use.LocationCanada.Time periodPre‐1880 AD to present.Major taxa studiedCladoceran zooplankton.MethodsAs part of the Natural Sciences and Engineering Research Council (NSERC) Canadian Lake Pulse Network, we selected 101 lakes across Canada along a gradient of human impact to analyse subfossil cladoceran assemblages from sediment cores. We examined relationships between taxonomic and functional indicators of cladoceran assemblage change among lakes and through time.ResultsContemporary assemblages were taxonomically and functionally less diverse locally relative to pre‐industrial assemblages (α‐diversity) and were structured by the degree of human impact in watersheds. Local α‐diversity losses were greatest in highly impacted lakes where agriculture and pasture are prevalent. While spatial homogenization (spatial β‐diversity) did not increase since pre‐industrial times as expected, temporal turnover (temporal β‐diversity) showed a non‐significant but increasing trend in highly impacted lakes, especially in urbanized watersheds.Main conclusionsCladoceran assemblages have changed significantly over the course of the Industrial period, and especially in more highly impacted watersheds, underscoring the important role of watershed land use in shaping diversity. However, indicators of cladoceran function have remained relatively conserved over time and land use change showed little impact on β‐diversity, despite important environmental variation. Overall, this research furthers our understanding of the health status of Canadian lakes and the consequences of human activities, especially agriculture and urbanization, on lake zooplankton.

The Effect of Land Use and Land Cover Changes on Flood Occurrence in Teunom Watershed, Aceh Jaya

The change in land use and land cover in upstream watersheds will change the features of drainage systems such that they will impact surface overflow and affect the infiltration capacity of a land surface, which is one of the factors that contributes to flooding. The key objective of this study is to identify vulnerable areas of flooding and to assess the causes of flooding using ground-based measurement, remote sensing data, and GIS-based flood risk mapping approaches for the flood hazard mapping of the Teunom watershed. The purposes of this investigation were to: (1) examine the level and characteristics of land use and land cover changes that occurred in the area between 2009 and 2019; (2) determine the impact of land use and land cover changes on the water overflow and infiltration capacity; and (3) produce flood risk maps for the Teunom sub-district. Landsat imagery of 2009, 2013, and 2019; slope maps; and field measurement soil characteristics data were utilized for this study. The results show a significant increase in the use of residential land, open land, rice fields, and wetlands (water bodies) and different infiltration rates that contribute to the variation of flood zone hazards. The Teunom watershed has a high and very high risk of ~11.98% of the total area, a moderate risk of 56.24%, and a low and very low risk of ~31.79%. The Teunom watershed generally has a high flood risk, with a total of ~68% of the area (moderate to very high risk). There was a substantial reduction in forest land, agricultural land, and shrubs from 2009 to 2019. Therefore, the segmentation of flood-risk zones is essential for preparation in the region. The study offers basic information about flood hazard areas for central governments, local governments, NGOs, and communities to intervene in preparedness, responses, and flood mitigation and recovery processes, respectively.

Quantifying the resilience of coldwater lake habitat to climate and land use change to prioritize watershed conservation

AbstractManaging ecological systems for resilience can increase their capacity to maintain key functions even under global change. Oxygenated coldwater (oxythermal) habitat in lakes is an important ecological resource that is threatened by both climate change and eutrophication. Here, we quantify the resilience of oxythermal habitat in over 10,000 glacial lakes in the upper Midwestern United States to climate change and watershed disturbance and classify lakes for conservation prioritization based on their current conditions and resilience. Oxythermal habitat was predicted by lake morphometry, July air temperatures, and watershed land use. Temperatures are projected to increase by mid‐century, and the magnitude of warming, its effect on oxythermal habitat, and the uncertainty surrounding that effect varied among lakes. Under mid‐century climate conditions, the number of lakes containing suitable coldwater habitat was predicted to decline by 67%, while the number of lakes with unsuitable habitat was predicted to increase by over 200%. Lakes varied in the amount of temperature increase that they could sustain without a resultant change in habitat tier (i.e., their climate resilience). Median climate resilience was 4.3°C, with some lakes capable of remaining in their habitat tier even with temperature increases up to 14°C. Changing watershed land use was predicted to influence oxythermal habitat in 24% of lakes (n = 2391). We used the magnitude of increase in watershed development that a lake could sustain while remaining in its current habitat class as a measure of its resilience to watershed disturbance. Conversely, decreased watershed development may improve oxythermal habitat conditions and push a lake into an improved condition, and this value represented a lake's restoration potential. We classified lakes into seven management classes based on their current oxythermal habitat conditions and the resilience of oxythermal habitat to climate and watershed disturbance. To facilitate management on individual lakes, we also assessed the vulnerability and resilience of individual lakes and the uncertainty surrounding these estimates. By quantifying the resilience of lakes and how it is influenced by local action across a multistate region, we can prioritize conservation action across multiple scales to maintain the critical habitat and ecosystem function of glacial lakes.

Influence of watershed land use on water quality in the state of Santa Catarina, Brazil

The inappropriate use of water resources by human actions compromises the balance between natural and anthropogenic factors. In this study, exploratory and field research were conducted with a scope of quantifying, based on satellite imaging, the use and occupation of land on the banks of the Itajaí-Açu River, the largest watercourse in the Itajaí River Basin, located in the State of Santa Catarina, Brazil. Five sampling points were allocated along the river at different times of the year to analyze water quality using chemical and biological indicators. The characterization of land use and occupation was carried out with Sentinel-2B satellite images at 10m resolution and QGIS software. Version 3.6.3 of the R Software was used to consolidate the data. The land use was categorized into several classes, the most representative of which was vegetation, which presented coverage of 34.42%, followed by the pastures and open fields class, with 27.83%, agriculture, with 18.18%, and urban areas, with 16.59% coverage. Our study showed that 62.6% of the river’s base was affected by anthropogenic influence, characterizing an environment severely altered from its normal state. The results obtained in the statistical analysis revealed a directional correlation between land use and water quality, thus indicating that cities on the banks of watercourses are major sources of potential contaminants. Among the classes of land use, the presence of vegetation along the riverside territory attenuated part of the load of pollutants launched into the Itajaí-Açu River. This finding highlights the importance of conserving the vegetation alongside the river to maintain water quality and, consequently, preserve the ecosystem’s biota.

Protist Diversity and Metabolic Strategy in Freshwater Lakes Are Shaped by Trophic State and Watershed Land Use on a Continental Scale.

ABSTRACTProtists play key roles in aquatic food webs as primary producers, predators, nutrient recyclers, and symbionts. However, a comprehensive view of protist diversity in freshwaters has been challenged by the immense environmental heterogeneity among lakes worldwide. We assessed protist diversity in the surface waters of 366 freshwater lakes across a north temperate to subarctic range covering nearly 8.4 million km2 of Canada. Sampled lakes represented broad gradients in size, trophic state, and watershed land use. Hypereutrophic lakes contained the least diverse and most distinct protist communities relative to nutrient-poor lakes. Greater taxonomic variation among eutrophic lakes was mainly a product of heterotroph and mixotroph diversity, whereas phototroph assemblages were more similar under high-nutrient conditions. Overall, local physicochemical factors, particularly ion and nutrient concentrations, elicited the strongest responses in community structure, far outweighing the effects of geographic gradients. Despite their contrasting distribution patterns, obligate phototroph and heterotroph turnover was predicted by an overlapping set of environmental factors, while the metabolic plasticity of mixotrophs may have made them less predictable. Notably, protist diversity was associated with variation in watershed soil pH and agricultural crop coverage, pointing to human impact on the land-water interface that has not been previously identified in studies on smaller scales. Our study exposes the importance of both within-lake and external watershed characteristics in explaining protist diversity and biogeography, critical information for further developing an understanding of how freshwater lakes and their watersheds are impacted by anthropogenic stressors.IMPORTANCE Freshwater lakes are experiencing rapid changes under accelerated anthropogenic stress and a warming climate. Microorganisms underpin aquatic food webs, yet little is known about how freshwater microbial communities are responding to human impact. Here, we assessed the diversity of protists and their myriad ecological roles in lakes varying in size across watersheds experiencing a range of land use pressures by leveraging data from a continental-scale survey of Canadian lakes. We found evidence of human impact on protist assemblages through an association with lake trophic state and extending to agricultural activity and soil characteristics in the surrounding watershed. Furthermore, trophic state appeared to explain the distributions of phototrophic and heterotrophic protists in contrasting ways. Our findings highlight the vulnerability of lake ecosystems to increased land use and the importance of assessing terrestrial interfaces to elucidate freshwater ecosystem dynamics.

ESTIMATION OF WATER BALANCE OF BARSACHHU WATERSHED IN CHUKHA BHUTAN USING REMOTE SENSING AND GIS

The water balance of a watershed is critical for the estimation of the water budget to meet the present and future domestic and economic demand and supply of water. Water balance parameters like precipitation, temperature, evapotranspiration soil moisture content deficit and surplus determine the water budget of a watershed which is further influenced by factors like land use, soil types, seasonal variation and other environmental factors. This paper intends to estimate the water balance of the Barsachhu watershed using Thornthwaite and Mather (TM) model. The use of Remote Sensing data and GIS as a tool were used in deriving the required data in executing the model. The study indicates that the monthly soil moisture content (deficit or surplus) is substantially influenced by the change in monthly rainfall, temperature and land use land cover pattern. April to October remain water surplus months while November to March remains a period of deficit. The soil moisture content has a different response to different land use in the Barsachhu watershed. The maximum annual moisture deficit and surplus of the basin are 126.27 mm and 2430.79 mm respectively and is observed in built-up areas. The runoff coefficient of the Barsachhu watershed computed from the runoff simulation of the TM model is 0.63.

Dynamics of land-use Change using Geospatial Techniques From 1986 to 2019: A Case Study of High Oum Er-Rbia Watershed (Middle Atlas Region)

This work aims to expose the contribution of the use of the cloud google earth Engine (GEE) platform, in particular the capacity of optical monitoring by remote sensing to assess the impact of environmental changes on the evolution of natural resources in the Middle Atlas region. To achieve this goal, the dense time stacking of multi-temporal Landsat images and random forest algorithm based on the Google Earth Engine (GEE) platform was used. The spatial resolution of the images used is 30 meters for the TM 5 sensor (Thematic Mapper) and the OLI 8 sensor (Operational Land Imager). Further, the google earth engine platform is used primarily to download and prepare the images for the dates 1986, 2000, and 2019, then a supervised classification with the Random Forest (RF) algorithm to produce land use maps of selected dates with an overall accuracy exceeding 80%. This was followed by the production of maps and change matrices for the periods 1986-2000 and 2000-2019. The results obtained have shown a decline in grassland, forest land, and water body in parallel with an increase in the following classes: buildings, farmland, and arboriculture during the last 30 years. In addition, elevation was the most important characteristic variable for land-use classification in the study area. Obtained results provide theoretical support for adjusting and optimizing land use in the High Oum Er-Rbia watershed.

Analisis Spasial Tekstur Tanah Terhadap Penilaian Risiko Bencana Hidrometeorologi di Kecamatan Rumbia-Kelara, Kabupaten Jeneponto

Soil texture is one of the keys to answering various soil susceptibility problems to hydrometeorological disasters in South Sulawesi. Some research results show a positive response related to the relationship between soil texture and hydrometeorological natural disasters. However, the spatial analysis of soil texture distribution in an area has not been widely associated with hydrometeorological disasters. This research aims to conduct spatial analysis related to the role of soil texture in hydrometeorological disasters (landslides and flash floods) with a case study in Kelara Watershed, Rumbia-Kelara District, Jeneponto Regency. In the topsoil and subsoil layers, samples were taken by purposive sampling in the Kelara watershed. Texture analysis was carried out using the hydrometer method, the distribution model of the soil texture fraction using the inverse distance weighting method, and the disaster risk assessment using the weighting method with field calculator. The dominant land use in the Kelara watershed is mixed dryland agriculture on a slope class of 25-45%. The dominance of soil texture in the Kelara watershed is the texture of silty clay loam to silty clay. The dominant clay fraction distribution in the upstream part of the Kelara watershed is 37.15-49.71%, so it has a reasonably high soil expansion power and can increase surface runoff. The distribution of silty fraction in the Kelara watershed area is evenly distributed in the upstream and central parts of the Kelara watershed area at 48.49-59.71%, causing the soil to be easily dispersed and triggering landslides-flashfloods. The level of susceptibility to landslide-flash floods in the Kelara watershed area in Jeneponto Regency has a very susceptible class of 63.21% of the total watershed area, which shows the high potential for landslide-flash floods. This potential requires mitigation measures to minimize disaster events and requires firm action from the local and central governments for the protection and utilization of upstream watershed areas in order to be sustainable.

Ecological risk assessment models for simulating impacts of land use and landscape pattern on ecosystem services

Rapid urbanization involves the expansion of construction land, which changes the land use and landscape pattern in watersheds. Moreover, it degrades ecosystem services and habitat quality, thus creating adverse ecological impacts such as the diffusion of non-point source (NPS) pollution. Therefore, it is urgent to investigate the adverse effects and potential ecological risks caused by variations in land use due to territory development and urbanization. Houxi Basin is a typical Chinese southeastern coastal watershed in the process of urbanization, and the ecological risk from 2011 to 2019 is here assessed. Based on ecosystem vulnerability and the interference with the ecosystem, we evaluated the risk of degradation of habitat services provided by terrestrial ecosystems due to changes in landscape patterns. In addition, the export coefficient model is employed to build an exposure-response relationship between land use and NPS pollution to investigate the risk of degrading water-purification services provided by aquatic ecosystems. The results show that the risks of degrading habitat-provision services increase slightly but for water-purification services increases rapidly. Alternatively, the integrated optimization scenario of key areas for 2030 reduces the risk of pollution diffusion and the landscape risk by 4.27% and 10.25%, respectively, compared with the business-as-usual scenario. In summary, reasonable planning of land-use types and spatial layout is conducive to reducing ecological risks. Other conclusions can be drawn: the combined replacement of forest and grassland more effectively inhibits pollution diffusion than does replacing only forest or only grassland. Optimizing areas with high land-use impact coefficients inhibits pollution diffusion more effectively than does optimizing areas with high export coefficients. Lastly, instead of increasing the area of green land, adjusting its spatial layout proves to be more effective in lowering the ecological risk to water-purification and habitat-provision services.

Exploring watershed effects on nutrient concentrations in shallow lakes through stable isotope analysis

Biogeochemistry patterns in shallow lakes are influenced by both in-lake factors such as ecosystem state as well as watershed-level factors such as land use, but the relative importance of in-lake versus watershed factors is poorly known. This knowledge gap makes it difficult for lake mangers to prioritize efforts on watershed versus in-lake strategies for stabilizing the clear-water state. We studied 48 shallow lakes in Minnesota, USA to assess the relative influence of lake size, land use in watersheds, and ecosystem state (turbid versus clear) on water column total nitrogen (TN) and total phosphorus (TP), as well as δ15N and δ13C in three species of fish. Our land use categories included natural areas, row crop agriculture, and all agriculture (row crops plus alfalfa). A model selection approach revealed different control mechanisms on the behavior of stable isotopes and nutrients. δ13C ratios in fish were most strongly influenced by lake size, while δ15N ratios were influenced by all agriculture in watersheds. In contrast, water column TN and TP concentrations were influenced by the in-lake factor of ecosystem state, with both nutrients lower in the clear state. We detected no effects of land use on TN or TP concentrations, likely due to strong effects of ecosystem state masking watershed effects. However, the strong relationship between agriculture and δ15N in fish indicated that watersheds did influence nutrient processing in shallow lakes, and that effects are not a legacy from past watershed events. Collectively, these observations indicate that lake managers should minimize agricultural intensity in shallow lake watersheds to facilitate the clear-water state, which will, in turn reduce water-column TN and TP relative to the turbid state.