Watershed Land Use Research Articles

Assessment of Soil Erodibility by using Geographic Information System

Deforestation and soil erosion are the uppermost environmental problems faced by the Kundahpalam watershed in Nilgiris hills. In this study, the area vulnerable to soil erosion associated with the soil inbuilt properties under different land use of Kundahpalam watershed were studied. Erosion modeling was performed using remote sensing and Geographic Information System (GIS) to achieve the best watershed management procedure for the study area. The Soil Erosion Index (SEI) was estimated with the dispersion ratio analyzed from soil properties of the study area. The hydraulic conductivity varied from 2.39 cm/h to 0.01 cm/h in the study area. Loam soil had the highest rate of hydraulic conductivity (2.395 cm/h). The clay soil had the lowest rate of hydraulic conductivity (0.01 cm/h). The water holding capacity varied from 43.54% to 56.39%. The clay loam had highest water holding capacity and loam had low water holding capacity in the study area. The dispersion ratio of the dense forest was found to be low (2.83). The built up land (3.91) and plantation land (3.35) have high dispersion ratio. From the results it is seen that, the erosion index of the built up land was low (2.12) because of hard terrain surface. The land without scrub (3.1) and plantation land (2.8) had high erosion index and these changes were attributed due to the soil properties. Based on the Middleton principle the soil present in the study area was found to be highly erodible in nature with respect to all land uses.

Modeling Hydrologic Response to Land Use and Climate Change in the Krueng Jreu Sub Watershed of Aceh Besar

Soil and Water Assessment Tool (SWAT) model was used to simulate impact of landuse and climate change on water resources in Krueng Jreu subwatershed located in Aceh Province – Indonesia. The subwatershed is a primary source of water to irrigated 233.52 km2 paddy field area through a surface irrigation system. The model performance was considerably good in predicting streamflow. The coefficients of determination varied between 0.58 and 0.72, while the Nash-Sutcliffe coefficients (ENS) ranged between 0.65-0.72 and the percentage bias were in the range of -0.36 to 2.30. Scenarios were applied to the best fit model to evaluate watershed responses to land use and climate changes. The model predicted increases in both runoff and water yield by 1% and 0.1% respectively as the result of increasing 15% settlement area. When all agricultural land within subwatershed converted to forest, water yield would increase by 1% during dry period and runoff contribution would decrease by 5%. Increases in surface flow by 23.6% and water yield by 15.1% were found under scenario of increasing 10% of daily precipitation. Increasing in evapotranspiration caused by an increase of 1.5⁰C in daily air temperature would decrease surface flow and water yield by 0.8% and 1.3%, respectively. Combination scenarios of changes in daily temperature and precipitation would increase evapotranspiration rate, annual water yield and runoff contribution.

Influence of land use and land cover patterns on seasonal water quality at multi-spatial scales

The influence of land use patterns on stream water quality is scale-dependent in space and time. Understanding the relationship between landscape characteristics and water quality is of great importance to improve water contamination prediction in unmonitored watersheds and for providing guidelines for watershed land use planning. In this study, five water sampling sites in the upper Dan River basin were established to monitor seasonal water chemical contamination over the period of 2000 to 2008. The relationships between land use patterns and water quality were analyzed across multiple-scales using redundancy analysis. The results showed that stream water quality variables displayed highly temporal variations, with electrical conductivity (EC), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−N), and total suspended solids (TSS) all generally displaying higher levels in the wet season, while there were higher concentrations of biochemical oxygen demand (BOD5), chemical oxygen demand (CODcr), and dissolved oxygen (DO) in the dry season. The total contribution of land use patterns on overall water quality was stronger at the riparian scale than at the catchment and reach scales during the wet season. However, different land use metrics had different scale effects. Urban land had a higher positive relationship with degraded water quality at small scales than at large scales, whereas agricultural land displayed the opposite scale effects. Forest and grassland explained more water quality variations at the riparian scale than at other scales. Analyses of spatial development patterns suggested that size, density, aggregation, and diversity of landscape patterns were important factors impacting on stream water quality. The results provide important information regarding sustainable land use and landscape planning at multiple-scales that can be used to improve water quality.

La descomposición de la hojarasca como herramienta para evaluar la integridad funcional de ríos altoandinos del sur del Ecuador

The ecological condition of tropical Andean rivers are threatened by many human activities including changes in land use and cover in watersheds. Current protocols diagnose the structural condition of streams but not their function. In this study we proposed an assessment tool using the leaf-litter breakdown as a measure of the functional condition and health of high Andean streams in Southern Ecuador, including methodology and threshold values adapted to local conditions. We selected 15 streams in three micro-basins (Mazán, Llaviuco and Matadero) within or in the vicinity of Cajas National Park where we deployed litterbags for 15, 28 and 64 days. We used two types of mesh (coarse and fine) for the litterbags in order to separate the contribution of macro-invertebrates and microorganisms in the decomposition process and also tested two different leaf substrates: Alder (Alnus acuminata) and Miconia (Miconia bracteolata). In each collection period we determined physical and chemical parameters, applied the riparian quality index (QBR-And) and river habitat index (IHF). Decomposition rates (-k) were determined from the time period at which approximately 50 % ash-free mass would have been lost. We used Ktotal and the ratio of the rate of decomposition between coarse and fine mesh (Kg/Kf) to define the functional condition thresholds. To test the metrics sensitivity we used graphical methods, one-way ANOVA and discriminative efficiency (ED). The analysis of watershed land-use and cover showed a gradient of intervention: Matadero ≥ Llaviuco > Mazán. The composition of the environmental variables of Mazán streams were different with respect to Llaviuco and Matadero, whose values were similar to each other. The QBR-And index showed a significant gradient from very low levels in Matadero (27.5), moderately high values in Llaviuco (66.5) to high values in Mazán (87). Alder leaf-litter breakdown rates were significantly faster in Mazán than in Matadero and Llaviuco streams, while breakdown rates of Miconia were not significantly different among watersheds. The Kg/Kf ratio was significantly higher in Mazán compared to Llaviuco and Matadero, which did not differ. We consider the Kg/Kf metric sensitive enough to discriminate impacts in the studied areas. Our results support the use of the leaf-litter breakdown as an appropriate tool to assess functional ecological condition, complementing the structural assessments of these Andean rivers.

The direct and indirect effects of watershed land use and soil type on stream water metal concentrations

The direct and indirect effects of watershed land use and soil type on stream water metal concentrations

Watershed Land Use and Seasonal Variation Constrain the Influence of Riparian Canopy Cover on Stream Ecosystem Metabolism.

Ecosystem metabolism is an important determinant of trophic structure, nutrient cycling, and other critical ecosystem processes in streams. Whereas watershed- and local-scale controls on stream metabolism have been independently investigated, little is known about how controls exerted at different scales interact to determine stream metabolic rates, particularly in urban streams and across seasons. To address this knowledge gap, we measured ecosystem metabolism in four urban and four reference streams in northern Kentucky, USA, with paired closed and open riparian canopies, during each of the four seasons. Gross primary production (GPP), ecosystem respiration, and net ecosystem production (NEP) were all best predicted by models with season as a main effect, but interactions between season, canopy, and watershed varied for each response. Urban streams exhibited higher GPP during most seasons, likely due to elevated nutrient loads. Open canopy reaches in both urban and forested streams, supported higher rates of GPP than the closed canopy which reaches during the summer and fall, when the overhead vegetation shaded the closed reaches. The effect of canopy cover on GPP was similar among urban and forested streams. The combination of watershed and local-scale controls resulted in urban streams that alternated between net heterotrophy (NEP <0) and net autotrophy (NEP >0) at the reach-scale during seasons with dense canopy cover. This finding has management relevance because net production can lead to accumulation of algal biomass and associated issues like nighttime hypoxia. Our study suggests that although watershed urbanization fundamentally alters ecosystem function, the preservation and restoration of canopied riparian zones can provide an important management tool at the local scale, with the strongest impacts on stream metabolism during summer.

Do waterbody classifications predict water quality?

Many states classify waterbodies according to groups of designated uses, which suggests that classifications may be correlated with water quality. The primary assessments of water quality in the United States (the Biennial Integrated Water Quality Reports) do not consider classification, so the relationship between classification and water quality is untested. Additionally, water quality has been shown to be influenced by watershed land use; however, land use is not typically part of waterbody classification systems. To determine the relationships between waterbody classification, water quality, watershed land cover, and forest fragmentation, we analyzed existing water quality data for the State of Connecticut from the United States Geological Survey and the Connecticut Department of Energy and Environmental Protection and land cover data from the National Land Cover Dataset. Connecticut uses a unique classification system that includes separation of drinking water sources (Class AA) and waterbodies receiving waste water discharges (Class B). Using a comparison of multiple means, we found that Class B waters had higher levels of nitrogen, solids, chloride, sodium, dissolved copper, total iron, and dissolved manganese than Class AA waters. Watersheds upstream of Class B segments had less forest cover, more development and more impervious cover than watersheds upstream of Class AA segments. Class A sites had some similarities in water quality and land cover with Class AA sites and some with Class B sites. The subset of Class B waterbodies with “Class AA-like” water quality also had “Class AA-like” land cover. Based on this and a multiple linear regression analysis, we found that water quality is more closely related to watershed land cover and forest fragmentation than to waterbody classification. Our results suggest that watershed land cover likely is a better proxy for water quality than waterbody classification.

A scenario approach to assess stakeholder preferences for ecosystem services in agricultural landscapes of Costa Rica

In many developing rural areas, efforts to avoid degradation of soil regulation services (SRS) face significant challenges especially in steep slopes due to the combined effect of climate change-related extreme precipitation and inadequate soil management practices in agriculture and grazing. In order to design socially desirable alternatives to the status quo, it is important to identify and engage relevant stakeholders to discuss the evaluation of land use and management alternative scenarios. However, innovative methods are needed to ensure the best use of available knowledge and often scarce data. We use structured value referendum (SVR) poll-type voting which is a value-focused decision-making process that can be used to create land use scenarios combining expert knowledge, modeling and stakeholders’ perspectives. We applied this approach to a Costa Rican watershed affected by heavy soil erosion. We engaged actors directly concerned with the on- and off-site effects of SRS degradation such as upstream farmers, a downstream hydropower facility affected by siltation and watershed planners. Results from preference elicitation regarding watershed land use scenarios showed that actors preferred alternatives to the status quo. They supported win–win land use strategies that protect SRS through soil conservation practices to be implemented in critical agricultural plots. Along with other land use scenario approaches that engage stakeholders, application of SVR can promote discussion and learning among interested parties and, at least in watershed conservation initiatives, can lead to identification of opportunities for joint gains among upstream land users and downstream users of soil- and water-related ecosystem services.

Non-point source pollution simulation under land use change scenarios in Hun-Taizi River watershed.

Non-point source (NPS) pollution has become a major source of water pollution in recent years. The research of NPS pollution mechanism and control has an important scientific and practical meaning. To study the effect of land use change on NPS pollution load, near future land use of Hun-Taizi River watershed was simulated under three scenarios based on CLUE-S model, including urban planning, historical trend and ecological protection scenarios. NPS pollution was simulated based on SWAT model. The simulated results of SWAT were compared with measured data. The response of NPS pollution to land use change and landscape pattern was studied with the combination of the two models in three land use scenarios. The results showed that the NPS pollution simu-lation with SWAT had high accuracy, which showed the suitability of SWAT model in the study area. The NPS pollution load increased under urban planning and historical trend scenarios but decreased under ecological protection scenario. The difference in three scenarios indicated that land use and landscape pattern impacted NPS to a certain extent, which showed that scientific ecological construction could effectively reduce NPS pollution load. This study provided a new study case for NPS pollution research at watershed scale, a scientific basis for implementation of non-point source pollution control and best management practices, and a reference for related policy making.

Spread of the native grass Elymus athericus in salt marshes of Mont-Saint-Michel bay as an unusual case of coastal eutrophication

Contrary to many estuaries where the increase in inputs of nitrogenous nutrients results in a macro-algal or phytoplanktonic bloom, no proliferation of this kind has ever been observed in the waters of Mont-Saint-Michel bay (north-western France) owing to a very high turbidity which greatly limits light penetration. On the other hand, it is well known that the factor that usually limits the growth of vascular plants in salt marshes is not the light resource but nitrogen availability; these plant species are therefore able to benefit fully from the enrichment of water by nitrogenous compounds. This seems to be the case of the sea couch grass Elymus athericus that has spread very rapidly on the salt marshes of this site since the mid-1980s. Firstly, the present study (i) accurately documents, from a compilation of data from administrative archives, the changes in agricultural land use in the major watersheds during the period 1970–2010, together with related changes in the nitrate contents of the rivers flowing into the bay; (ii) quantifies the spatial spread of sea couch grass between 1984 and 2013 from the five maps made during this period. In the second part, using in-depth analysis based on the findings of previous studies, it shows that the expansion of this native grass corresponds to a biological invasion phenomenon, for which nitrogen enrichment of the bay seems to be the only plausible explanation.

Estimating watershed degradation over the last century and its impact on water-treatment costs for the world’s large cities

Urban water systems are impacted by land use within their source watersheds, as it affects raw water quality and thus the costs of water treatment. However, global estimates of the effect of land cover change on urban water-treatment costs have been hampered by a lack of global information on urban source watersheds. Here, we use a unique map of the urban source watersheds for 309 large cities (population > 750,000), combined with long-term data on anthropogenic land-use change in their source watersheds and data on water-treatment costs. We show that anthropogenic activity is highly correlated with sediment and nutrient pollution levels, which is in turn highly correlated with treatment costs. Over our study period (1900-2005), median population density has increased by a factor of 5.4 in urban source watersheds, whereas ranching and cropland use have increased by a factor of 3.4 and 2.0, respectively. Nearly all (90%) of urban source watersheds have had some level of watershed degradation, with the average pollutant yield of urban source watersheds increasing by 40% for sediment, 47% for phosphorus, and 119% for nitrogen. We estimate the degradation of watersheds over our study period has impacted treatment costs for 29% of cities globally, with operation and maintenance costs for impacted cities increasing on average by 53 ± 5% and replacement capital costs increasing by 44 ± 14%. We discuss why this widespread degradation might be occurring, and strategies cities have used to slow natural land cover loss.

Detecting long-term temporal trends in sediment-bound trace metals from urbanised catchments

The shift from rural lifestyles to urban living has dramatically altered the way humans interact and live across the globe. With over 50% of the world’s populations living within cities, and significant increases expected over the next 50 years, it is critical that changes to social, economic and environmental sustainability of cities globally be implicit. Protecting and enhancing aquatic ecosystems, which provide important ecosystem services, is challenging. A number of factors influence pollutants in urban waterways including changes in land-use, impervious area and stormwater discharges, with sediment-bound pollution a major issue worldwide. This work aimed to investigate the spatial and temporal distribution of trace metals in freshwater sediments from six urbanised catchment over a 30-year period. It provides an estimate of pollution using a geoaccumulation index and examines possible toxicity using a probable effect concentration quotient (mPECq). Results showed significant temporal changes in metal concentrations over time, with lead generally decreasing in all but one of the sites, attributed to significant changes in environmental policies and the active elimination of lead products. Temporal changes in other metals were variable and likely dependent on site-specific factors. While it is likely that diffuse pollution is driving changes in zinc, for metals such as lead, chromium and copper, it is likely that watershed landuse and/or point sources are more important. The results clearly indicated that changes to watershed landuse, environmental policy and pollution abatement programs are all driving changes in sediment quality, highlighting the utility of long-term sediment monitoring for assessment of urban watershed condition. While this study has demonstrated the utility of detecting long-term changes in metal concentrations, this approach could easily be adapted to detect and assess future trends in other hydrophobic contaminants and emerging chemicals of concern, such as synthetic pyrethroids, providing essential information for the protection of catchment.

Rice Mapping Using RADARSAT-2 Dual- and Quad-Pol Data in a Complex Land-Use Watershed: Cau River Basin (Vietnam)

The strong temporal backscatter signature of rice growing above the water's surface allows for the use of synthetic aperture radar (SAR) for paddy rice crop mapping in Southern Vietnam (Mekong Delta). In Northern Vietnam (Red River Delta), rice mapping using SAR is a challenge and is rarely performed because of the complex land-use/land-cover. Nevertheless, information about rice fields is needed for hydrological simulations in river basins such as the Cau River basin. The objective of this research is to investigate the potential of RADARSAT-2 band- C in identifying rice fields over a large and fragmented land-use area. Two methods are proposed, one for each data type, adapted to the land-use/land-cover of the study area. The thresholding technique, with a statistical analysis of the temporal variation of rice backscattering, was applied to the HH like-polarized ratio of dual-pol data. The support vector machine (SVM) algorithm was applied to the full quad-pol and a single HH-polarization calculated from polarimetric data. This study demonstrates that RADARSAT-2 dual- and quad-pol data can be successfully used to identify cultivated rice fields. However, the dual-pol data seems less efficient than the quad-pol data and the SVM classification is more flexible than the thresholding technique. Between the full quad-pol and a single polarization, the overall classification accuracy shows that the results derived from the single HH polarization are 3 to 10% less accurate than those derived from the classification of full quad-pol data. The results show the usefulness of polarimetric C -band data for the identification of rice fields in Northern Vietnam.

Land use influence on raw surface water quality and treatment costs for drinking supply in São Paulo State (Brazil)

Anthropogenic disturbances to the environment can compromise valuable ecosystem services, including the provision of potable water. These disturbances decrease water quality, potentially increasing treatment costs for producing drinking water. We investigated the land use influence on raw surface water quality for drinking supply in the most populous state in Brazil (São Paulo). We analyzed a long-term dataset (2000–2014) to assess the raw water quality for drinking purposes in more than 50 river/stream sites located in predominantly industrial/urban, agriculture or forested watersheds. Temporal, seasonal and land cover influences were assessed through Analysis of Covariance (ANCOVA). Infrastructure and operating costs of the Water Treatment Plants (WTPs) were estimated. We found significantly better water quality (p<0.01, ANCOVA) in forested watersheds (e.g., mean turbidity and true color: 10 NTU and 14mgPt/L versus 48–56 NTU and 38–49mgPt/L in industrial/urban and agriculture areas). THMPF and TOC were greater in altered basins (304μg/L and 5.8mg/L, respectively), especially in the rainy season. Drinking water outputs varied across WTPs located in industrial/urban (average: 525L/s), agriculture (392L/s) and forest (167L/s) watersheds. Infrastructure and operating costs, shown as cost per unit of capacity, were greater for plants located in forested areas (US$ 98,208 per L/s), as compared to industrial/urban (US$ 78,230 per L/s) and agriculture (US$ 75,332 per L/s) basins. This was probably because treatment costs in these locations were greater in spite of plants starting with higher quality water. We recommend upgrades in the existing WTPs and the construction of new water utilities consider treatment costs related to predicted changes in land use in supply watersheds. Watershed conservation practices, water demand management, remediation and adaptation actions could also lower treatment costs and alter optimal treatment technology choice.

Spatial Response of River Water Quality to Watershed Land Use Type and Pattern Under Different Rainfall Intensities

Qixiang River watershed, as a typical case study area, was divided into five types of buffer zones according to elevation and slope. Based on the remote sensing images, DEM and real-time monitoring data in April, May, June 2015, the relationship between land use type and pattern in all buffer zones and water quality under different rainfall intensities was explored. The results showed that land use type and pattern in different buffer zones had obvious discrepancies. The proportion of construction land was the highest in low flat area, secondary flat area and high flat area. The main land use type of moderately steep area and high steep area was forest land. Secondly, the low flat area appeared to have the greatest influence on the water quality. Thirdly, construction land had a greater influence on water quality than other land use types in low flat area. In addition, in secondary flat area, wetland was the key factor under small rainfall intensity. However, construction land was the key factor under moderate rainfall intensity and large rainfall intensity. In moderately steep area and high buffer zones, construction land influenced the water quality most under small rainfall intensity but forest land was the greatest factor under moderate rainfall intensity and large rainfall intensity. Fourthly, the relationship between the land use pattern and water quality was complicated. SH-MN had the greatest influence on water quality and the influence increased with increasing rainfall intensity in low flat area. Furthermore, PD, SH-MN and SHDI were the key factors in secondary flat area while SH-MN, SHDI and PD were the key factors in high flat area under all the three types of rainfall intensity. SH-MN and CONTAG influenced the water quality most in moderately steep area and high steep area under small and high rainfall intensity. CONTAG influenced the water quality most in moderately steep area and SHDI was the key factor in high steep area under moderate rainfall intensity.

Performance of the Phytoplankton Index for Lakes (IPLAC): A multimetric phytoplankton index to assess the ecological status of water bodies in France

A new phytoplankton-based index was designed to respond to the Water Framework Directive (WFD) requirements concerning the assessment of lake ecological status. The “Indice Phytoplancton Lacustre” (IPLAC) is a multimetric index, taking into account biomass, abundance and species composition of communities. The first metric is based on the total phytoplankton biomass (MBA), the second on the abundance and taxonomic composition (MCS) of 165 indicator taxa. The IPLAC was developed on 2 independent databases, one for the calibration and the second for the validation of the metrics. The calibration dataset was composed of 255 “lake-years” from 214 distinct lakes sampled between 2005 and 2012. The validation dataset included 173 lake-years in order to confirm the response of the index to the trophic gradient and anthropogenic pressure.The results show that the IPLAC correctly highlights chemical pressure (eutrophication). Especially high Pearson correlations are shown with total phosphorus (r=−0.71, p-value<0.001), chlorophyll-a (r=−0.83, p-value<0.001) and water transparency (r=0.73, p-value<0.001) which are the main proxies for the trophic level. Corine land cover was used as an indication of the anthropogenic pressure and good correlations are also found with the watershed land use, negatively correlated with agricultural area (r=−0.60, p-value <0.001), population density (r=−0.36, p-value <0.001) and positively with forest area (r=0.57, p-value <0.001).The index is WFD-compliant and is dedicated to natural lakes and artificial water bodies in metropolitan France, and will be routinely used by the French Ministry of the Environment to assess lake ecological status through the phytoplankton community. However, the results must be carefully interpreted in two cases: reservoirs with large water level fluctuations, and samples that include less than 5 indicator species.

Estimation of Runoff for Ozat Catchment using RS and GIS Based SCS-CN Method

Estimation of runoff in a watershed is a prerequisite for design of hydraulic structures, reservoir operation and for soil erosion control measures. Water resource planning and management is important and critical issue in arid and semi-arid regions. Runoff from a watershed affected by several geo-morphological parameters and for a particular watershed land use change can affect the runoff volume and runoff rate significantly. Several methods are investigated to estimate the surface runoff from a catchment but the Curve Number method is mostly used. Present study was undertaken to estimate surface runoff and water availability for two sites (Ozat-2 and Zanzesri) in the Ozat catchment situated in Junagadh, Gujarat, India using RS and GIS based curve number method. The Weight curve number for the ozat catchment is 73.00. The correlation coefficient between calculated and observed runoff was good for both catchments. In this study found that SCS-curve number method along with RS and GIS can be used successfully in semi-arid region to simulate rainfall runoff and to estimate total surface water.

Fingerprints of upstream catchment land use in suspended particulate organic matter (SPOM) at the river discharge sites in Lake Victoria (Kenya): insights from element, stable isotope and lipid biomarker analysis

Riverine transport and discharge are the primary pathways for terrigenous organic matter (OM) input to lacustrine environment. Understanding the influence of catchment land use on the source, composition and fate of terrigenous particulate OM in a lake is therefore vital. We used C/N, δ13C, δ15N and lipid biomarkers in the suspended particulate OM (SPOM) at the seven river discharge sites in Lake Victoria, in an effort to evaluate the potential of upstream catchment land use on the biogeochemistry of SPOM. The total fatty acids (FAs), alcohols and sterols in SPOM ranged from 4.61 to 7.42 μg/g, 1.52 to 3.32 μg/g and 3.01 to 5.81 μg/g respectively. At sites receiving discharge from industrial effluent the FAs were dominated by short chain FAs (SCFAs), polyunsaturated FAs (PUFAs), monounsaturated FA (MUFAs) and branched FAs (brFAs); the alcohols were dominated by short chain alcohols (SCOHs) and phytol; sterols were dominated by 27Δ5, 27Δ0, 28Δ5,22, 28Δ5, which are associated either with phytoplankton or zooplankton. Sites receiving discharge from substantial agricultural activity in the catchment were dominated by long chain FAs (LCFAs), long chain alcohols (LCOHs) and 29Δ5,22 and 29Δ5 sterols, reflecting vascular plant terrigenous input. There was also evidence of OM from mixed autochthonous and allochthonous sources at the sites regardless of the upstream catchment land use activities. The findings suggest that human land use in upstream watersheds affect the source, composition and distribution of SPOM discharged by rivers, which may not only impact nutrient cycling in the lacustrine environment, but may also change the quality of SPOM.

A Comparative Assessment of Runoff Nitrogen from Turf, Forest, Meadow, and Mixed Landuse Watersheds

AbstractLandscaping paradigms that encourage high‐input, intensively managed and mono‐culture turf/lawn landscapes have raised concerns about water quality. We conducted a watershed‐scale assessment of landscaping practices that included turf, urban, forest, native meadow, and mixed landuse watersheds with a professional golf course and a parking lot. The turf site was moderately managed and had lower fertilizer inputs than those typically used by homeowners and golf courses. Stream water sampling was performed during base flow and storm events. Highest nitrate and total nitrogen concentrations in runoff were observed for the mixed watershed draining the golf course. In contrast, concentrations in base flow from the turf watershed were lower than expected and were comparable to those measured in the surrounding meadow and forest sites. Total nitrogen concentrations from the turf site increased sharply during the first storms following fertilization, suggesting that despite optimal management there exists a risk for nutrient runoff following fertilization. Overall, this study suggests that turf or lawns, when managed properly, pose minimal water quality risk to surface waters. Rate, timing of application, and the type of fertilizer appear to be the key factors affecting water quality. Better education of homeowners and landscaping professionals with regard to these factors may be a cost‐effective strategy to reduce nonpoint source pollution.

Watershed Land Use and Local Habitat: Implications for Habitat Assessment

Our understanding of anthropogenic stressor effects on wetland biota and ecosystem processes would benefit from better defined relationships between landscape and local stressors. We assessed the connection between watershed land use and local habitat and local disturbance in Great Lakes coastal ecosystems across a full range of anthropogenic stress. In addition, we identified dominant structuring variables, described redundancy, and assessed the relative influence of local versus watershed scale features on local habitat quality with on-site assessments conducted at 143 sample sites. Associations between habitat variables and watershed stressors were found, but only a small proportion of variation was explained. Overall, watershed agriculture was a stronger predictor of local habitat variables than was development. Variance partitioning revealed that disturbance and land use accounted for more variance in habitat than spatial factors or wetland type. This indicates that local and watershed-scale assessments are discrete approaches that document stress at different hierarchical scales and an assumed direct connection between watershed stress and local habitat and disturbance is an over-simplification. Therefore, assessments of stress should include both watershed scale and on-site habitat assessments. Furthermore, these results indicate that local scale mitigation/restoration could minimize negative impacts of changing land use.