Catchment Research Research Articles

Featured data sources and normalised indices of use in small Arctic catchments research

The development of remote sensing instruments and methods has revolutionised work practices worldwide, resulting in a new field of research. Remote sensing has significantly expanded the possibilities for detailed research, spanning from biological to urban studies, by constantly imaging the Earth. Numerous photogrammetric campaigns and satellite missions have been increasing the possibilities for conducting research that includes larger areas and time scales while minimising the need for fieldwork. This is particularly useful in polar regions, where fieldwork is complicated by harsh weather conditions, hard-to-reach research areas, polar nights, and the need for high funding and logistical support. Here available algorithms that help to track environmental shifts in the small Arctic catchments, such as changes in ice, snow, vegetation, and water are presented.

The bioavailability of particulate nitrogen in eroded sediment: Catchment sources and processes

PurposeAnthropogenic land use change has caused an increase in particulate nutrient loads from catchments draining to the Great Barrier Reef (GBR). The research in GBR catchments has indicated that particulate nutrients are bioavailable to both freshwater and marine phytoplankton, but relative importance of this source of nutrients to the GBR is unknown. We quantified the contribution of this source of bioavailable nitrogen in a dry-tropics grazing and a wet-tropics fertilized mixed land use catchment of the GBR.Materials and methodsThe different bioavailable nitrogen pools and associated processes through which dissolved inorganic nitrogen (DIN) is generated from eroded sediment (mass of DIN generated per mass of sediment) were identified. These pools and processes were quantified from a range of representative sediment sources (e.g. surface and subsurface soil and different land uses). We collected 17 sediment source samples in the wet tropics and 41 in the dry tropics. We combined the N pool concentration data with spatial and hydrological fine sediment modelling to estimate the contribution from different sources and processes/pools to the end-of-catchment DIN load.Results and discussionThe modelled load of DIN generated from sediment accounted for all the monitored DIN load in the grazing-dominated catchment but was insignificant in the fertilized mixed land use catchment. Sediment from surface erosion (hillslope erosion) and some soil types contributed disproportionally to the modelled DIN generation. Fast solubilisation of DIN was the main process in the catchments studied. The importance of mineralisation of the organic fraction increased with the time the sediment was in suspension.ConclusionParticulate nutrients in sediment are a significant source of bioavailable nitrogen in eroding grazing catchments. The processes that drive this bioavailability are complex, vary with sediment source and operate at different timeframes and spatial scales.

Estimating evapotranspiration using earth observation data: A comparison between hydrological and energy balance modelling approaches

• Earth observation data is a useful alternate data source to hydrological models. • The spatial resolution of satellite data affects the accuracy of evapotranspiration. • The Surface Energy Balance System model outperformed the ACRU model. • Hydrological models should be developed to allow actual evapotranspiration input. Hydrological models are often applied to acquire estimates of evapotranspiration ( ET a ) using quality inputs of reference evapotranspiration ( ET 0 ). However, their application may be limited by the need for good quality long-term data inputs. In data scarce regions, the use of satellite-earth observation data as inputs to these models may provide a potential solution to overcome data acquisition challenges associated with conventional data collection approaches. In this study, the Agricultural Catchments Research Unit (ACRU) hydrological model was applied to estimate the ET a using both in-situ and satellite-derived estimates of ET 0 as inputs to the model. The simulated ET a estimates were then evaluated through comparisons against field-based measurements of ET a acquired from an Eddy Covariance system ( EC ET ), as well as from the application of the Surface Energy Balance System (SEBS) model. The results of these investigations demonstrated that the meteorologically-based ACRU ET a simulations marginally outperformed the satellite-based ACRU ET a simulations. While these results highlight the influence which the quality of ET 0 inputs may have on the accuracy of the ACRU derived ET a estimates, the concurrent application and evaluation of SEBS demonstrated that alternate approaches to hydrological modelling, may be better suited for ET a estimation in certain instances.

Seasonal local rainfall and hydrological forecasting for Limpopo communities – A pragmatic approach

This paper describes the development and testing of a simple local seasonal forecast system of rainfall and hydrological conditions. The primary target group is agricultural extension officers who communicate forecasts to small-scale farmers at local level. Two pilot areas within the Limpopo river basin in South Africa were used, one in the Luvuvhu river basin in Vhembe district and the other in the Letaba river basin in Mopani district. Local rainfall and hydrological forecasts of runoff, soil moisture and evapotranspiration were produced, built on readily available deterministic seasonal meteorological forecasts for large-scale rainfall from CSIR (Council for Scientific and Industrial Research, South Africa), produced from an ensemble of seasonal forecasts using the CCAM (Conformal-Cubic Atmospheric Model) global forecast model. Hydrological forecasts were produced through a “proxy” approach, whereby outputs from the ACRU (Agricultural Catchment Research Unit) agrohydrological model provided expected hydrological responses from observed years that are representative of the rainfall anomalies predicted by the global seasonal forecast. Locally monitored soil moisture augmented the hydrological forecasts. The local seasonal forecast system does not require sophisticated calculations or a complex operational environment and complements coarser scale forecasts disseminated by the provincial departments of agriculture. Results of three rainfall seasons from 2013 to 2016 in the pilot areas showed the proxy approach to have relatively good matches between forecasts and available observations, showing better predictability for below normal rainfall seasons with exception for an extreme monthly rainfall event. The forecasts matched observed conditions best during the strong El Niño phase of ENSO (El Niño Southern Oscillation) for 2015/2016.

A commentary on ecohydrology as a science-policy interface in implementing the UN Sustainable Development Goals

Ecohydrology, as an integrating discipline, can contribute strongly to achieving the Sustainable Development Goals (SDGs) especially in the context of Integrated Water Resources Management (IWRM). Using ecohydrology principles in applying IWRM affords a better understanding of the links between water, biodiversity, and human wellbeing in the catchments. One problem with the SDGs is that they are presented in a “silo” style, which means there are few if any connections between SDG6 “clean water and sanitation” and SDG 15 “life on land”, which deals with wetlands and catchments. Ecohydrology principles, drawing on the need to better understand green and blue infrastructure, can help bridge between the SDGs in an IWRM context, allowing thus for their more successful achievement.The Convention on Wetlands (Ramsar, 1971) has degrees of overlap and redundancy with the UNECE Water Convention (1992). And both rely on better science, policy, and management of catchments for effective implementation. Ecohydrology can help promote and develop the science base of these Multilateral Environment Agreements allowing for interpretation of catchment processes and dynamics, and thus better application of IWRM, and ultimately better policies for management of water resources, and thus alleviation of water scarcity.Ecohydrology can also play a role in fostering social science research in catchments, heritage management and conservation. So far in UNESCO, ecohydrology has been largely dealt with by the International Hydrological Programme, in the Division of Water Sciences. There is a future role for ecohydrology as a cross-cutting theme across all UNESCO Sectors, led by the Natural Sciences Sector.

Hydrological trends and the evolution of catchment research in the Alptal valley, central Switzerland

AbstractWhen the observation of small headwater catchments in the pre‐Alpine Alptal valley (central Switzerland) started in the late 1960s, the researchers were mainly interested in questions related to floods and forest management. Investigations of geomorphological processes in the steep torrent channels followed in the 1980s, along with detailed observations of biogeochemical and ecohydrological processes in individual forest stands. More recently, research in the Alptal has addressed the impacts of climate change on water supply and runoff generation. In this article, we describe, for the first time, the evolution of catchment research at Alptal, and present new analyses of long‐term trends and short‐term hydrologic behaviour. Hydrometeorological time series from the past 50 years show substantial interannual variability, but only minimal long‐term trends, except for the ~2°C increase in mean annual air temperature over the 50‐year period, and a corresponding shift towards earlier snowmelt. Similar to previous studies in larger Alpine catchments, the decadal variations in mean annual runoff in Alptal's small research catchments reflect the long‐term variability in annual precipitation. In the Alptal valley, the most evident hydrological trends were observed in late spring and are related to the substantial change in the duration of the snow cover. Streamflow and water quality are highly variable within and between hydrological events, suggesting rapid shifts in flow pathways and mixing, as well as changing connectivity of runoff‐generating areas. This overview illustrates how catchment research in the Alptal has evolved in response to changing societal concerns and emerging scientific questions.

In-situ soil moisture data improve seasonal streamflow forecast accuracy in rainfall-dominated watersheds

Seasonal streamflow forecasting methods are less skillful in rainfall-dominated catchments than snow-dominated catchments, where measurements of water storage in the snowpack enhance predictability. Recent research in snow-dominated catchments showed that forecasts can be further enhanced by also including soil moisture measurements, but the impact of soil moisture data on forecast performance in rainfall-dominated watersheds remains unknown. Our objective was to evaluate the potential improvements gained by including in-situ soil moisture data in seasonal streamflow forecasting models in rainfall-dominated watersheds. Precipitation and soil moisture data from four watersheds in the U.S. were incorporated into a modified principal components analysis and regression method to predict seasonal (4-month) streamflow totals at 0-, 1-, 2-, and 3-month lead times. Forecasts derived from antecedent precipitation alone were often statistically insignificant and explained less than 30% of the variance in seasonal streamflow, as indicated by the Nash-Sutcliffe efficiency coefficient. Conversely, forecast models that included soil moisture information explained up to 87% of seasonal streamflow variance at the 0-month lead time, up to 81% at the 1-month lead time, up to 71% at the 2-month lead time, and up to 52% at the 3-month lead time. The root mean square errors for forecasts which included soil moisture data were on average 55% lower than for those based on antecedent precipitation alone. The soil moisture-based forecasts for rainfall-dominated watersheds exhibited accuracies comparable to those previously reported in snow-dominated watersheds. This new forecast method shows strong potential for use in surface water management in rainfall-dominated regions.

Verification of runoff volume, peak discharge and sediment yield simulated using the ACRU model for bare fallow and sugarcane fields

The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual agrohydrological model with various applications, design hydrology being one of them. Model verification is a measure of model performance and streamflow, soil water content and sediment yield simulated by the ACRU model have been extensively verified against observed data in southern Africa and internationally. The primary objective of this study was to verify simulated runoff volume, peak discharge and sediment yield against observed data from small catchments, under both bare fallow conditions and sugarcane production, which were located at La Mercy in South Africa. The study area comprised 4 research catchments, 101, 102, 103 and 104, monitored both under bare fallow conditions and sugarcane production, with different management practices per catchment. Observed data comprised: daily rainfall, maximum and minimum temperature, A-pan evaporation and runoff for the period 1978–1995, and peak discharge and sediment yield for the period 1984–1995. The data were checked for errors and and inconsistent records excluded from analysis. Runoff volume, peak discharge and sediment yield were simulated with the ACRU model and verified against the respective observed data. In general, the correlations between observed and simulated daily runoff volumes and peak discharge were acceptable (i.e. slopes of regression lines close to unity, R2 ≥ 0.6 and the Nash–Sutcliffe coefficient of efficiency close to unity). Similarly, the correlation between observed and simulated sediment yield was also good. From the results obtained, it is concluded that the ACRU model is suitable for the simulation of runoff volume, peak discharge and sediment yield from catchments under both bare fallow and sugarcane land cover in South Africa.

Verification of runoff volume, peak discharge and sediment yield simulated using the ACRU model for bare fallow and sugarcane fields

The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual agrohydrological model with various applications, design hydrology being one of them. Model verification is a measure of model performance and streamflow, soil water content and sediment yield simulated by the ACRU model have been extensively verified against observed data in southern Africa and internationally. The primary objective of this study was to verify simulated runoff volume, peak discharge and sediment yield against observed data from small catchments, under both bare fallow conditions and sugarcane production, which were located at La Mercy in South Africa. The study area comprised 4 research catchments, 101, 102, 103 and 104, monitored both under bare fallow conditions and sugarcane production, with different management practices per catchment. Observed data comprised: daily rainfall, maximum and minimum temperature, A-pan evaporation and runoff for the period 1978–1995, and peak discharge and sediment yield for the period 1984–1995. The data were checked for errors and and inconsistent records excluded from analysis. Runoff volume, peak discharge and sediment yield were simulated with the ACRU model and verified against the respective observed data. In general, the correlations between observed and simulated daily runoff volumes and peak discharge were acceptable (i.e. slopes of regression lines close to unity, R2 ≥ 0.6 and the Nash–Sutcliffe coefficient of efficiency close to unity). Similarly, the correlation between observed and simulated sediment yield was also good. From the results obtained, it is concluded that the ACRU model is suitable for the simulation of runoff volume, peak discharge and sediment yield from catchments under both bare fallow and sugarcane land cover in South Africa.

Calcium and strontium isotope dynamics in three polluted forest ecosystems of the Czech Republic, Central Europe

Calcium and strontium isotope ratios were used to identify Ca sources for bulk soil, soil solutions and runoff in the stressed forest ecosystems of Central Europe. All three study sites are underlain by Ca-poor crystalline bedrock (orthogneiss, leucogranite and serpentinite, respectively), but differ in historical rates of acid deposition. UDL, the spruce die-back affected site at the Czech–Polish border underlain by orthogneiss, received six times more acidifying compounds from the atmosphere than LYS and PLB, two paired catchments near the Czech–German border. The paired catchments near the Czech–German border, whose forests were only mildly damaged by industrial pollution, differ in their acid buffering capacity (extremely low for LYS leucogranite, extremely high for PLB serpentinite). At the spruce die-back affected catchment UDL, 19 years of monthly hydrochemical monitoring revealed six times higher atmospheric deposition and runoff fluxes of Ca, compared to the paired catchments LYS and PLB. Across the three sites, the mean δ44Ca values increased in the order: spruce bark (−0.84‰) < spruce xylem (−0.31‰) < spruce fine roots (0.0‰) < bedrock (0.08‰) < soil (0.11‰) < spruce needles (0.31‰) < open-area precipitation (0.68‰) < spruce throughfall (0.71‰) < runoff (0.74‰) < soil water (1.11‰). At all three sites, Ca from atmospheric deposition was isotopically similar to Ca in runoff, indicating export of recent atmospheric Ca. All three catchments had isotopically lighter Ca in silicate bedrock and exported isotopically heavier Ca via runoff. Trees mostly represented the isotopically lightest Ca pool, whereas soil water collected by lysimeters contained isotopically heavy Ca. The 87Sr/86Sr isotope ratios were nearly uniform at the serpentinite site PLB (0.710). The 87Sr/86Sr ratios across the two felsic sites (UDL and LYS) increased in the order: open-area precipitation (0.710) < spruce canopy throughfall (0.715) < spruce xylem (0.723) < spruce needles (0.725) < soil water (0.734) < runoff (0.740) < soil (0.862) < bedrock (0.881). Collectively, the δ44Ca and 87Sr/86Sr isotope systematics indicated that organic Ca cycling, along with atmospheric input of isotopically heavy Ca, largely contributed to the high-δ44Ca values of runoff. The studied silicate bedrock had significantly lower δ44Ca values than the reported world-wide average. While bulk soil Ca was likely affected by bedrock Ca even after the period of acid rain, the δ44Ca difference between soil and soil water indicated a major role of recycled organic Ca in supplying nutrition to the trees. Future Ca-Sr isotope research in headwater catchments should include isotope analysis of sequentially leached Ca fractions from weathered minerals in soil to better assess the geogenic Ca inputs to runoff. In catchments currently recovering from pollution, Ca-Sr isotope fingerprinting of dust emitted from coal-fired power plants will be needed. Isotope analysis of local coal can indicate to what extent Ca-Sr isotope composition of past deposition contributes to the isotope signatures of present-day runoff.

Application of Vertical Electrical Sounding (VES) Method with Resistivity Meter Based on Boost Converter to Estimate the Potential of Groundwater Aquifers in Karang Anyar of Tarakan City

Water catchment research has been done in Karang Anyar of Tarakan City with the aim to estimate the potential of groundwater aquifers. Groundwater is more widely used to meet the needs because of its better quality compared to surface water. The groundwater distribution is not only described vertically, to find horizontally can be seen through the deployment of geological formations that act as aquifers. Vertical Electrical Sounding method is one method that can be used to predict geological and hydrogeological conditions. Based on geoelectric exploration using a resistivity meter based on boost converter shows the presence of groundwater in a depth of 7. 91-_44. 33 meters with resistance of 27. 22 Ωm and the estimated lithology is sand. According the research could determine that resources ground water in Karang Anyar village is prospectly.

Modeling Soil Erosion and Landscape Metric Analysis of River Catchments in Pulau Pinang, Malaysia

To determine the soil erosion in ungauged catchments, the author used 2 methods: Universal Soil Loss Equation model and sampling data. Sampling data were used to verify and validate data from model. Changing land use due to human activities will affect soil erosion. Land use has changed significantly during the last century in Pulau Pinang. The main rapid changes are related to agriculture, settlement, and urbanization. Because soil erosion depends on surface runoff, which is regulated by the structure of land use and brought about through changes in slope length, land-use changes are one of many factors influencing land degradation caused by erosion. The Universal Soil Loss Equation was used to estimate past soil erosion based on land uses from 1974 to 2012. Results indicated a significant increase in three land-use categories: forestry, built-up areas, and agriculture. Another method to evaluate land use changes in this study was by using landscape metrics analysis. The mean patch size of built-up area and forest increased, while agriculture land use decreased from 48.82 patches in 1974 to 22.46 patches in 2012. Soil erosion increased from an estimated 110.18 ton/km2/year in 1974 to an estimated 122.44 ton/km2/year in 2012. Soil erosion is highly related (R2 = 0.97) to the Shannon Diversity Index, which describes the diversity in land-use composition in river basins. The Shannon Diversity Index also increased between 1974 and 2012. The findings from this study can be used for future reference and for ungauged catchment research studies.

Investigation of System Design Criteria and the Capital Cost of Varying Design Return Periods for Soil and Water Conservation Structures

Highlights Very few sediment yield events contribute to annual sediment yield. Any rainfall, runoff, and peak discharge event has the potential to generate the most extreme sediment yield event. Twenty year return period recommended for design of conservation structures. Abstract . Design of conservation structures includes both hydrologic and hydraulic designs. Hydrologic design involves estimation of design floods which are required for the sizing of the hydraulic structures. The minimum recommended return period for the design of conservation structures is 10 years but due to the projected levels of risk, and the fact that a few large events are likely to be responsible for the majority of the erosion, the 10-year return period currently recommended may be inadequate. This study investigated system design criteria and the capital cost of varying design return periods for soil and water conservation structures in the sugar industry of South Africa. Observed rainfall data and results of runoff, peak discharge and sediment yield simulated using the Agricultural Catchments Research Unit (ACRU) model were utilized in this study. Relationships between extreme events of sediment yield and the rainfall, runoff and peak discharge events associated with them were analyzed and the capital cost of varying design return periods was also investigated. The results showed that only 0.2% of sediment yield events contributed up to 95% of the annual sediment yield simulated in the sugar production areas in South Africa and that any event of rainfall, runoff and peak discharge had the potential to generate an extreme sediment yield event provided the soil surface was not adequately protected. Based on a sustainable soil loss of 5 t ha-1, the 20-year return period was recommended for the design of soil and water conservation structures. Furthermore, the capital cost implication of varying design return periods from the minimum 10-year return period ranged from an increase of 16% to 35% across the sugar industry. Therefore, given that soil erosion is associated with adverse effects on sustainable crop production and also increases in costs of replanting destroyed crops, the 20-year return period is recommended for the design of soil and water conservation structures in the sugar industry in South Africa. Keywords: Capital cost, Design criteria, Erosion, Return perioW, Risk, Soil and water conservation.

Interpreting nested storm event suspended sediment‐discharge hysteresis relationships at large catchment scales

AbstractReducing soil erosion and sediment delivery into rivers is a major aim for land management in New Zealand. Therefore, it is important to identify areas of sediment generation and their relationship to in‐stream suspended sediment concentrations and water quality attributes. It is possible to infer and assess sediment sources and dynamics using storm event suspended sediment concentration‐discharge hysteresis shape and loop direction. Research in small catchments has achieved some success; however, research in larger (&gt;103 km2) catchments has shown the inherent difficulty of interpreting hysteresis patterns at larger scales. In this paper, we use a nested, long‐term suspended sediment monitoring program across a large catchment (3,903 km2: Manawatū in New Zealand) to address these challenges. We evaluate the hysteresis patterns of five major tributaries (subcatchment areas 329–1,298 km2) of the Manawatū River together with the hysteresis patterns at the gauged catchment outlet. Hysteresis patterns of the Manawatū subcatchments can be characterized as predominantly clockwise, that is, high hysteresis index (HI) value. Larger storms (discharge &gt;2 × 107 m3) increase the likelihood of clockwise hysteresis directions, whereas smaller storms (discharge &lt;2 × 107 m3) are more likely to be anticlockwise. The link between suspended sediment concentration‐discharge hysteresis and subcatchment sediment sources becomes increasingly attenuated within the larger subcatchments. High antecedent discharge negatively correlates to HI values, suggesting conditions immediately before the storm have an influence on whether the catchment is “primed” or “exhausted” with available sediment. The different storm categories indicate that within this catchment, whereas hysteresis patterns vary due to the spatial origin of discharge and sediment to some extent, storm magnitude has a stronger impact on hysteresis dynamics than spatial origin.

The relevance of hydrological research in small catchments – A perspective from long-term monitoring sites in Europe

The usefulness of small (&lt; 10 km2) catchments has been repeatedly recognized during the recent history of hydrological research. This foreword to the special issue of Cuadernos de Investigación Geográfica – Geographical Research Letters devoted to long term hydrological research in small catchment in Europe highlights the main reasons for promoting the small catchment approach and revises its growing use, starting with the first catchment studies in Switzerland for management purposes, and followed by the development of more interdisciplinary research programs that used small catchments as field laboratories, long-term observatories, sites for method and model validation, and places for training young researchers. The volume includes nine contributions concerning studies carried out in long term monitoring sites in several European countries and aims at showing the relevance of the small catchment approach in hydrological research in Europe.

Runoff generation in a pre-alpine catchment: A discussion between a tracer and a shallow groundwater hydrologist

Runoff generation mechanisms vary between catchments and despite decades of research in many catchments, these mechanisms are still not fully understood. In this paper, runoff generation mechanisms in the steep pre-alpine catchments in the Alptal, Switzerland, are discussed. These fast responding catchments are characterized by low permeability soils on top of flysch bedrock. In combination with the high and frequent precipitation, this results in predominantly wet conditions. In many areas, the water table is close to the surface. We review the main results of recent (2009-2016) studies in these catchments that used isotope, stream chemistry and hydrometric data. These field studies focused on the spatial and temporal patterns in groundwater levels, spatial patterns in the isotopic composition and chemistry of streamflow during baseflow conditions, as well as the responses of streamflow and its isotopic composition during rainfall events. The combined results of these studies highlight the establishment of connectivity of areas with a different topographic position and areas with a different land use during rainfall events. They also show the importance of flow in higher conductivity near surface soil layers for runoff generation, as well as the frequent occurrence of surface runoff. Spatial differences in groundwater dynamics are related to topography. Streamflow responses are mainly affected by the rainfall characteristics; differences in streamflow and hydrochemistry between catchments with different portions of forest, meadows and wetlands, were relatively small. However, variations in the chemistry of baseflow along stream reaches within a catchment were considerable. Above all, these studies highlight the value of combining data on spatial patterns of groundwater levels and stream chemistry with long term data on streamflow to derive a more complete picture of the dominant runoff generation mechanisms.

Assessing Impacts of Land Use Changes on the Hydrology of a Lowland Rainforest Catchment in Ghana, West Africa

Impact assessments of actual and potential land use (LU) changes on hydrology are vital in land use planning, which is a prerequisite for effective water resources management. In this study, impacts of actual, as well as potential, LU changes on the hydrology of the Bonsa catchment (1482 km2), Ghana, West Africa, were assessed using the Agricultural Catchments Research Unit (ACRU) hydrological model. Baseline, current and potential future LU maps for three scenarios, namely, business-as-usual (BAU), economic growth (EG) and economic growth and reforestation (EGR), driven by observed climate between 1990 and 2009, were used for the study. The results indicate that peak and dry season streamflows between 1991 and 2011 have increased by 21% and 37%, respectively, under the current land use in comparison to the baseline due to a decrease in evergreen and secondary forests by 18% and 39%, respectively, and an increase in settlements, mining areas and shrubs/farms by 81%, 310% and 343%, respectively. The potential future LU scenarios suggest that there may be further increases in streamflows, but the historical land use changes between 1991 and 2011 were so substantial that they will continue to impact streamflow changes in any of the future land use scenarios. The study also showed that variability of streamflow changes at the catchment scale was lower than at the subcatchment scale. For the scenarios of potential future LU changes, the BAU shows the highest increases in streamflows, while the EGR shows the least. Policy interventions for effective management of the catchment are recommended.

Application of the Proportion of Sediment‐sensitive Invertebrates (PSI) biomonitoring index

AbstractSedimentation of river beds is a key pressure impacting riverine ecological communities. Research has identified the need for new approaches to help demonstrate and quantify the impacts of excessive fine‐sediment deposition on benthic macroinvertebrate populations. To help meet this requirement, the Proportion of Sediment‐sensitive Invertebrates (PSI) methodology was developed and has been in operational use in the United Kingdom for several years. This paper presents a number of case studies, at both national and local scales, showing how the method can be used to identify point and nonpoint fine‐sediment pollution, as well as demonstrating the analysis of a national dataset to describe the relationship between PSI and a channel substrate index. A novel approach to displaying PSI data alongside local ecological and hydrological information is also presented and interpreted, to illustrate how improved understanding of biotic and abiotic relationships and interactions can be readily accomplished. Excessive fine‐sediment accumulation on river beds results in impaired ecosystem health globally. The case studies and examples presented here will provide confidence that the PSI method can form the basis for evidence gathering and analysis, both within and beyond the United Kingdom. The paper concludes with an overview of the use of PSI in catchment research and management, a consideration of the relationship of the metric with other macroinvertebrate indices, and a summary of refinements recently applied to the index.

Evaluation of runoff response on the basis of a comparative paired research in mountain catchments with the different land use: case study of the Blanice River, Czechia

The paper evaluates the runoff response in two small mountain catchments on the basis of a comparative paired research in the headwater area of the Blanice River, south Bohemia. The predominantly grassy Zbytinský potok and forested Tetřívčí potok brooks represent the headwaters landscape of the eastern part of the Šumava Mountains. Differences in runoff response are observed on the principle of black box from the two points of view: long-term water balance characteristics and rainfall-runoff events. Despite the average lower runoff values, the forested Tetřívčí potok brook showed a more significant runoff response in most events, mainly in wet years, and the total higher variability of runoff. It has a significantly higher runoff during a dry period. The research is based on the own data obtained by continual monitoring of the water level, discharge and precipitation. The presented study wants to assess the differences in the behaviour of both hydrological systems, especially their response to a causal rainfall.

Modelling hydrological processes, crop yields and NPS pollution in a small sub-tropical catchment in South Africa using ACRU-NPS

The Agricultural Catchment Research Unit—Nitrates, Phosphorous and Sediments (ACRU-NPS) model, which simulates runoff, sediment and nutrient (NO3 and P) production in agricultural catchments, is used to evaluate the impact of farming practices and land-use changes on crop yields, water discharge, sediment and nutrient loads in the 41-km2 Mkabela catchment in the KwaZulu-Natal midlands, South Africa. The ACRU-NPS model was modified with the following objectives: (a) to develop and incorporate algorithms to simulate crop growth and NPS pollution dynamics in process zones and control features; (b) simulate sediment and nutrient production from land segments for various land uses; (c) model crop yield where crop growth is influenced by water and nitrogen stress; and (d) simulate sediment and nutrient fate at controls and buffers in the stream network. Five management practice scenarios were simulated and run with a series of fertilizer management applications. The resulting crop yields, water discharge, sediment and nutrient loadings were analysed. On average, doubling fertilizer application from base rates resulted in the highest sugarcane yield increase of 5 t/ha, zero fertilizer application resulted in the highest sugarcane yield reduction of 11 t/ha, while applying deficit irrigation, with base fertilizer application rates retained, resulted in 16 t/ha sugarcane yield increase. Flood attenuation and retention capacities for the total non-point source (NPS) pollutants for the period 2006–2012 were also investigated in the study area.