Grass Filter Research Articles

The Relationship between Erosion and Precipitation and the Effects of Different Riparian Practices on Soil and Total-P Losses via Streambank Erosion in Small Streams in Iowa, USA

Streambank erosion in agricultural landscapes contributes high amounts of sediment and total-P to surface water, resulting in the degradation of stream habitats and reduction in ecological services. Moreover, the implication of future climate change on bank erosion is also a growing concern. Streambank erosion rates from riparian forest buffers (RFo), grass filters (GFi), row-crops (RCr) and pastures, including fenced pastures (FPa), rotationally grazed pastures (RPa), intensive rotationally grazed pastures (IPa), and continuously grazed pastures (CPa), in three landform regions of Iowa, were measured over seven years. Bank erosion pins were measured seasonally (spring, summer and fall) in the first five years (2002–2006) and yearly for two more years (2007–2008). It was found that summer and spring seasons are the important ones since the relationships between erosion and precipitation were significantly “strong” in almost all the riparian practices, and precipitation was found to be the main factor driving streambank erosion. Streambank mean soil losses and soil total-P losses from RFo (23.3 tons km−1 yr−1 and 9.8 kg km−1 yr−1, respectively), GFi (31.1 and 9.9) and FPa (44.0 and 23.7) practices were all significantly lower than the grazing pasture practices, including RPa (142.3 and 58), CPa (255 and 105.1), IPa (234.6 and 122.7) and RCr fields (352.9 and 118.9). Also, RPa had significantly lower total-P loss than CPa, IPa and RCr practices (RFo, GFi, FPa < RPa < CPa, IPa, RCr). RCr practices had the highest streambank soil losses among all other riparian practices (RFo, GFi, FPa < RPa < IPa, CPa < RCr). The study showed that riparian conservation practices (RFo, GFi and FPa) showcased significant benefits in mitigating streambank soil loss and associated soil total-P load to streams. However, their effectiveness is highly sensitive to changing climatic conditions and the extent of spatiotemporal variations.

The effect of planting grass filter strips on fishes in agricultural headwater streams

Abstract Grass filter strips (i.e., herbaceous riparian buffers) are a widely used conservation practice in the United States to mitigate the impacts of agriculture on streams and rivers. Yet, only a limited amount of information is available on the effects of grass filter strips on stream fishes and instream habitat conditions and long‐term assessments are rare. The objective of this research was to document the long‐term effects of planting grass filter strips adjacent to channelized agricultural headwater streams on fish community structure and instream habitat. Fishes, instream habitat and riparian characteristics were sampled from three channelized agricultural headwater streams without grass filter strips, three channelized agricultural headwater streams with grass filter strips and two unchannelized streams having forested riparian habitats in central Ohio from spring of 2006 to autumn of 2015. Fish species richness, abundance, darter species richness, per cent darters, sunfish species richness, minnow species richness and per cent headwater fishes did not differ among riparian habitat types. Darter species richness and per cent darters differed annually. Mean water depth, velocity, wetted width, instream habitat diversity, dominant grain size and per cent instream wood did not differ among riparian habitat types. Mean water depth, water velocity, wetted width and instream habitat diversity exhibited annual differences. Additionally, mean riparian width, woody vegetation density and per cent canopy cover were greater in forested streams than the unplanted and grass filter strip streams. Riparian characteristics did not differ annually. The lack of fish community responses 10–13 years after planting grass filter strips is probably due to the lack of corresponding changes in hydrological characteristics, substrate and instream wood amounts. These results suggest that grass filter strips should not be implemented alone but in conjunction with conservation practices that will improve physical habitat quality and water quality.

A framework for applying interceptive mitigations for diffuse agricultural pollution

ABSTRACT Interceptive mitigation options implemented at the edge of agricultural fields and along run-off and drainage flow-paths can complement preventive in-field management actions to reduce diffuse contaminant losses to surface waters. However, it is often unclear to users which interceptive mitigation option is appropriate for their situation, where it should be located, what contaminant reductions and other benefits can be achieved, and what it would cost to implement, maintain, and operate these practices. We outline a framework for selecting and applying eight interceptive diffuse pollution mitigation practices potentially applicable on New Zealand farms: riparian grass filter, planted and multifunction buffers; constructed wetlands; woodchip bioreactors; filamentous algal nutrient scrubbers; sediment traps; and detainment bunds. The framework provides users with a semi-quantitative evaluation of the relative benefits and costs of the best suited mitigations across a range of farmed landscapes. It highlights where each mitigation has its niche in terms of the landscape fit, flow-path(s) intercepted, contaminant(s) targeted, efficacy, associated co-benefits, relative cost, operation and maintenance requirements, longevity, and consenting requirements. Testing and refinement of this framework is encouraged, using data from field-scale implementation, to better quantify efficacy in practice, and inform empirical models and decision making across farm and catchment scales.

Evaluating the Effects of Riparian Habitat Type on Nutrient Concentrations in Agricultural Headwater Streams

ABSTRACTGrass filter strips and other riparian buffer types are frequently used in agricultural watersheds to reduce nonpoint source pollution, but there is only limited information available on their long‐term watershed scale effects. Our research questions were as follows: (1) does nutrient concentrations differ among agricultural headwater streams with different riparian habitat types? and (2) does the effect of riparian habitat type differ annually or seasonally? Eight streams in central Ohio were selected based on watershed size, proportion of watershed agricultural land use, and riparian habitat type. Three streams possessed unplanted riparian habitats, three streams had grass filter strips, and two streams had forested riparian habitats. Water samples for the measurement of ammonia, nitrate + nitrite, total nitrogen, dissolved reactive phosphorus, total phosphorus, and dissolved organic carbon concentrations were collected weekly from two sites in each stream from March 2007 to February 2017. Mean nitrogen and phosphorus concentrations did not differ (p > 0.05) among riparian habitat types. Mean dissolved organic carbon concentrations exhibited different (p < 0.05) annual and seasonal trends among riparian habitat types. Our results indicated that planting grass filter strips alone may not decrease nitrogen and phosphorus concentrations and highlighted the influence of riparian woody vegetation on the temporal dynamics of dissolved organic carbon concentrations.

Effect of selected bioengineering measures on runoff, soil loss, and cotton (Gossypium hirsutum L.) productivity in the semi-arid region of western India

Soil erosion and associated loss of soil nutrients and organic carbon are one of the major reasons for low crop productivity in major cotton (Gossypium hirsutum L.) growing areas of India. This calls for designing acceptable and low-cost bioengineering measures to enhance system productivity and soil health. Thus, a field study was conducted at Vasad, Gujarat, India from 2014 to 2017 to evaluate the efficacy of selected bioengineering treatments on cotton crop production and runoff and soil loss. The eight experimental treatments consisted of bio-filters of three grass species, viz.Para (Brachiaria mutica), Guinea (Megathyrsus maximus),and Napier (Pennisetum purpureum) at two strip widths (1 m and 2 m), field bund, and the conventional system as practiced by the farmers of the region. The treatments were tested in 45 × 10 m plots having the gauging facility for recording runoff and soil loss data. Rainfall, runoff, sediment concentration, soil loss, organic carbon, nutrient loss, and growth and yield parameters of grass barrier species and the cotton crop were recorded and analysed. The filter strip of Guinea sp. at 2 m width was most effective, reducing runoff by 30%, soil loss by 66%, nutrients loss by 69%, sediment concentration to 1/3rd, and soil organic carbon loss by 65%. The lowest runoff coefficient value of 0.209 observed among the filter strips in this treatment, indicated about 79% of rainwater was conserved in situ. The available soil nutrients increased by up to 42% and SOC concentration by 61%, and cotton equivalent yield by 25% than that of the conventional system. We concluded that Guinea grass filter strips of 2 m width planted at 45 m spacing in cultivable lands having 2% slope minimized runoff, soil loss, nutrient loss, improved soil fertility and enhanced cotton productivity.

Nitrogen credit trading as an incentive for riparian buffer establishment on Pennsylvania farmland

Agricultural nitrogen loading is a leading cause of eutrophication within the Chesapeake Bay. Agriculture in the Commonwealth of Pennsylvania is responsible for a large portion of the nitrogen load entering the bay. Vegetated riparian buffers are a common agroforestry practice used to intercept surface runoff and subsurface leaching of nutrients such as nitrogen from upland agricultural fields. Watershed-wide nutrient credit trading has been suggested as a mechanism for reducing nutrient pollution entering the Chesapeake Bay. The cost of producing nitrogen credits through the establishment of riparian buffers on Pennsylvania farmland was analyzed to determine if nitrogen credit trading could provide an incentive for buffer establishment. Forest buffers were shown to have marginally lower nitrogen credit production costs and payback periods than grass filter strips. Larger riparian buffers were shown to have higher credit production costs than smaller buffers due to increases in establishment costs outpacing increases in nitrogen credit trading revenue. Nitrogen credit trading was determined to be an inadequate incentive for agricultural riparian buffer establishment due to the high cost of producing nitrogen credits. Furthermore, nitrogen credit trading was shown to be less lucrative compared to the Conservation Reserve Enhancement Program, a common riparian buffer cost share program. However, increases in the market price of nitrogen credits or bundling nitrogen with other nutrient credits such as phosphorus could ultimately result in credit trading providing an adequate incentive for agricultural riparian buffer establishment. These results could be used to guide the framework for nutrient credit trading programs within other watersheds.

Understanding stream bank erosion and deposition in Iowa, USA: A seven year study along streams in different regions with different riparian land-uses

Agricultural activities such as row-cropping and grazing, have accelerated stream bank erosion. Accelerated stream bank erosion increases nonpoint source pollutants in aquatic ecosystems, significantly degrading them. Mitigating stream bank erosion is a priority worldwide, especially in agricultural watersheds. The objective of this study was to analyze the impacts of riparian land-use management on stream bank erosion and deposition, along with analyzing its temporal and spatial patterns. The study was conducted in three regions of Iowa (central, northeast and southeast) along 30 stream reaches adjacent to seven different riparian land-uses. The riparian land-uses were riparian forest buffers, grass filters, pastures with the cattle excluded from the stream, intensive rotational grazing, rotational grazing, continuous grazing and row crop fields. Seasonal erosion and deposition data (Spring, Summer and Autumn) were collected along these reaches for 5 years and yearly for the following two years. To analyze the data, conventional statistical methods (ANOVA and Tukey's test) along with innovative techniques (percentile plots, cumulative erosion curves and bubble charts) were utilized. Based on the analysis, of this extensive in time (seven years) and large in size (1500 pins measured 17 times in three regions) field dataset, major results were obtained in regard to stream bank erosion in Iowa, USA. Stream banks exhibited high year-to-year variation in erosion and deposition showcasing the need for long-term datasets to better understand stream bank erosion and deposition. Seasonal erosion, also had high variability with Spring recording the most erosion followed by Summer and Autumn. Certain seasons exhibited high stream bank erosion indicating that managers need to focus on these seasons, to reduce erosion effectively. In addition, seasonal measurements can highlight depositional events that might be masked with annual measurements. Riparian land-uses significantly impacted stream bank erosion. Riparian forest buffers and grass filters significantly mitigated stream bank erosion while traditional agricultural practices like continuous grazing and row-crop agriculture had accelerated stream bank erosion. Finally, the percentile plots, cumulative erosion curves and bubble charts captured some stream bank responses that would have been unnoticed using conventional statistical methods, allowing decision makers, stakeholders and the general public, to support and approve measures to mitigate this environmental problem. Nature-based solutions utilizing riparian perennial vegetation can sustainably mitigate stream bank erosion.

Development of a novel framework for modeling field-scale conservation effects of depressional wetlands in agricultural landscapes

The intermixed cropland, grassland, and wetland ecosystems of the upper mid-western United States combine to provide a suite of valuable ecological services. Grassland and wetland losses in the upper midwestern United States have been extensive, but government-funded conservation programs have protected and restored hundreds of thousands of acres of wetland and grassland habitat in the region. The value of restored wetlands in agricultural fields is complex, and the USDA Natural Resource Conservation Service, Conservation Effects Assessment Project (CEAP) has been lacking the methodology to include these conservation practices in their analyses. Our aim is to develop a reproducible methodology for simulating wetlands within the CEAP cropland modeling framework used to evaluate other agricultural conservation practices. Furthermore, we evaluate the effect of using upland conservation practices on the functioning of restored wetlands. By simulating the addition of a depressional wetland that effectively removes 6% of the field from crop production, we obtained a 15% reduction in annual runoff and a 29% and 28% reduction in mean annual nitrogen (N) and phosphorus (P) losses, respectively. The presence of the depressional wetland in the field is estimated to also reduce edge-of-field losses of sediments by 20% and sediment-bound N and P by 19% and 23%, respectively. Additionally, adding a grass filter strip around the wetland greatly decreased sediment inputs to the wetland, increasing the effective life of the wetland, in terms of its ability to perform valued services, by decades to centuries. Our method for modeling depressional wetlands embedded in cropped fields provides a means to quantify the effects of wetland conservation practices on field-level losses for regional assessments, such as the CEAP.

Portable and efficient graphene-oxide based multistage filtration unit for water purification

In recent times, ensuring availability of adequate supply of potable water for its citizens is of great concern for nations across the globe. Water purification is a matter of high immediacy in developing countries, where enough supply of clean drinking water is unavailable. Globally, in consideration of the water-related diseases, assurance of an affordable, scalable water treatment infrastructure is of paramount significance. Many states in India face are confronted by scarcity of safe water and pollution, evoked mainly by anthropogenic activities. Majority of the population is unable to either access or afford safe drinking water. More than 60% of this population rely on groundwater for the purpose of drinking alone and on surface waters for all other purposes. In this era of high-water necessity, the aim of this paper is to develop a handy personal, water purifier, which is a ubiquitous, cost-effective access to healthy potable water for humans. This portable water purifier is a multi-stage filter constituted of a fabric filter, graphene-oxide coated sand filter, vetiver grass filter, and a UV filtration system. Water quality test show drastic reductions in the total dissolved solids (TDS), hardness, chloride and calcium ions. Implementation of this filtration unit in water-stressed countries is expected to serve as an efficient and affordable appliance for daily consumption of water.

Neighbor effects on adoption of conservation practices: cases of grass filter systems and injecting manure

Animal feeding operations are significant nonpoint source polluters for water resources in the USA, through leaching of nutrients applied as manure or chemical fertilizers. Voluntary adoption of nutrient management practices, such as grass filter systems and injecting manure into soil, has been promoted to minimize the nutrient leaching from livestock operations. Previous studies that analyzed the adoption of conservation practices faced difficulties in explaining the adoption of such practices using the variables primarily identified to explain the adoption of profit-oriented technologies. The objective of this study is to analyze the social aspect of the adoption of conservation practices. We specifically analyzed the neighbor effect on the adoption of grass filter systems and injecting manure into soil. We found that farmers who have a neighbor using a grass filter system were more likely to adopt grass filters than farmers who did not have such a neighbor. The explanatory power of the regression model doubled when the neighbor effect was included. Hence, programs and policies to promote the adoption of conservation practices should take into account the social capital aspect of the neighbor effect.

Riparian Land-Use Impacts on Stream Bank and Gully Erosion in Agricultural Watersheds: What We Have Learned

Stream bank and gully erosion are major sources of nonpoint source pollutants, especially in landscapes dominated by agriculture. Implementation of upland conservation practices in landscapes dominated by agriculture reduces upland sediment transport more than water runoff, leading to excessive stream bank and gully erosion. This review focus on ten different studies conducted in streams in Iowa that investigated riparian land-use impacts on stream banks, gullies, and other riparian sediment sources (cattle loafing areas and cattle stream access points). The riparian land-uses investigated were riparian forest buffers; grass filters; continuous, rotational, and intensive rotational pastures; pastures with cattle fenced out of the stream; and row-cropped fields. Results of these studies indicate that maintaining perennial deep-rooted vegetation in riparian areas and excluding cattle from the stream channel stabilizes stream banks and gullies. Cattle loafing areas and cattle stream access points appear to also be important sediment sources. Re-establishing perennial riparian vegetation is a sustainable and cost-effective conservation practice because it reduces sediment in streams while maintaining the majority of the watershed in agricultural production. The limited available funds for the implementation of holistic watershed conservation practices suggest using targeted approaches, at the watershed scale, to improve conservation practice effectiveness.

Grass filter strip residence time‐trap efficiency relationship

AbstractThis paper investigates the relationship between trap efficiency and residence time in vegetative filter strips under unsteady flow conditions. A mathematical model, based on a kinematic‐wave formulation of overland flow and a mass balance equation for suspended sediments, is employed. An empirical equation is used to estimate sediment removal. The governing equations are written and solved numerically in terms of a set of dimensionless variables. The results indicate that the relationships between the trap efficiency and residence time depend on the shape of the inflow hydrograph. Further analysis of results identified another non‐dimensional parameter that can predict the trap efficiency if only the volume and the peak rate of inflow are known. While the mathematical model employed includes many elements of the sophisticated vegetative filter strip models previously reported, the resulting charts are as easy to use as the oversimplified design methods currently in use

Performance of Grass Filter Strip in Copper and Zinc Removal in Surface and Subsurface Runoff

Three filter strips were conducted on self-designed soil bins. Taking a filter strip with no vegetation as contrast, the effectiveness of vegetation and soil conditions on heavy metals (including copper and zinc) removal efficiencies were investigated by simulated runoff experiment. The results showed that the adsorbed state is the main existing form of heavy metal. For surface runoff, most of total copper and total zinc are trapped in first 4m and it is ineffective to increase the distance beyond 4m for removal. Vegetation has no significant effect on total copper and total zinc removal, while the soil with higher content of organic matter is contributing to total Zn interception. For subsurface runoff, the removal efficiencies of total copper and total zinc can reach to above 95.38% and both vegetation and soil conditions have no significant effects. Vegetation is contributing to copper ion and zinc ion removal significantly. Soil condition is only a significant factor to zinc ion, with higher content of organic matter as a contributing factor.

Hydrologic design aid for urban grass filter strips

AbstractA set of generalised charts are presented in this article as a design aid for hydrologic sizing of grass filter strips. The charts express the volume of runoff and the peak flow rate from a grass strip and the residence time in terms of the size and surface and subsurface characteristics of the grass strip as well as the size and surface characteristics of the area draining to the filter strip. These charts are developed by using a mathematical model based on a kinematic‐wave formulation of overland flow and Green‐and‐Ampt formulation for infiltration. The results are obtained in terms of dimensionless parameters and generalised through the principle of hydrologic similarity. An example is included to demonstrate the use of the charts in a practical design problem.

Soil Fauna Diversity Relationship with NO3Content in Grass Filter Strips within Intensive Agriculture Land

ABSTRACT The biodiversity is a core value in all ecosystems. The nitrogen (N) addition in the form of N fertilizers has effect to a wide variety of fauna living in soils. N losses from arable land should tend not only to cause water eutrophication, but also lower soil nutrient stocks and decreasing soil fertility. This study determined the effect of N soil content in conventional tillage agro-ecosystem on the soil fauna diversity in grass stripes under the sloped arable land. My objective here is to observe soil faunal taxa living in grass filter strips. The goal of this work is to describe the relationship of soil fauna to the nitrate (NO3 -) content runoff from fields and captured in grass filter strips. The field work was carried out during period from May until June 2013, for soil fauna investigation the extraction in Berlese — Tullgren funnels were used. Nitratenitrogen (NO3-N) was extracted from air-dried sieved soil using a 2 M KCl solution. Altogether 2,020 specimens representing 19 arthropod grou...

Planting grass filter strips: Does it influence the structure and function of riparian habitats of agricultural headwater streams?

AbstractGrass filter strips are strips of cool or warm season grasses planted adjacent to agricultural streams to reduce nutrient, pesticide, and sediment input. This conservation practice is the most frequently planted riparian buffer type in the United States. Previous studies have not evaluated how grass filter strips alter the structure and function of riparian habitats of agricultural streams. Our objective was to examine the research hypothesis that planting grass filter strips will influence the structure and function of riparian habitats of channelized agricultural headwater streams. We sampled riparian vegetation, quantified coarse particulate organic matter input and nutrient input, and measured water temperature within two unplanted riparian habitat sites, two riparian habitat with grass filter strips sites, and two forested riparian habitat sites of agricultural headwater streams in central Ohio. Forested riparian habitats exhibited greater percent maximum frequency of woody vegetation and reduced water temperatures than unplanted riparian habitats and grass filter strips. Forested riparian habitats also exhibited greater canopy cover, woody vegetation taxa richness, and coarse particulate organic matter input than grass filter strips and greater riparian widths and woody vegetation abundance than unplanted riparian habitats. Grass filter strips did not differ in structure and function from unplanted riparian habitats. We conclude that planting grass filter strips does not influence the structure and function of riparian habitats of channelized agricultural headwater streams.

Effectiveness of Dichanthium annulatum in Watercourses for Reducing Sediment Delivery from Agricultural Watersheds

A field experiment was conducted to determine the efficacy of Dichantium annulatum grass filters in watercourses and to optimize the grass coverage in these watercourses. This experiment was conducted in 2% slope watercourses with varying filter grass coverage (0, 25, 50, 75, 100%) as main treatments and different flow rates (5, 10, 15, 20 L/s) as sub‐treatments. The inflow and outflow, flow velocity, depth of the flow, and sediment concentration was measured and analyzed for each run. The experimental results reveal that the grass filter strips are able to reduce the sediment concentration in the runoff water by six times (from 4.2 to 0.65 g/L). The filter strips are able to reduce the velocity of the runoff water by two times (from 1.06 to 0.47 m/s) and convert the supercritical flows into subcritical flows. The filter strips are able to increase the Manning's coefficient from 0.0323 to 0.1006 under various discharges. From the experiment, it can be concluded that more than 50% grass filter coverage in watercourses did not further reduce sediment concentration, outflow, flow velocity, and the Froude number and increase roughness of the channels. Based on these results, it is recommended that D. annulatum can be used as a filter in watercourses to prevent runoff and soil losses from crop fields and thereby reducing the sedimentation of downstream water bodies. The optimum grass coverage, i.e. 50% of the channel length, can maintain the maximum grass production with minimum soil loss.

Riparian land-use impacts on bank erosion and deposition of an incised stream in north-central Iowa, USA

Stream bank erosion and deposition are complex phenomena because of the many factors that influence them. These factors can be spatial such as bank aspect, height and slope or temporal such as seasonal and yearly precipitation and streamflow events. Riparian land-use also has a major influence. This study investigated for two years, spatial and temporal patterns and dominant geomorphologic processes of stream bank erosion and deposition along a 10km reach of Bear Creek in north-central Iowa, USA. The channel sub-reaches used were adjacent to a riparian forest buffer, a perennial grass filter and a continuously grazed pasture. Two plots were placed in each sub-reach; one on a north-facing outside bank (north-bank) and the other on a south-facing outside bank (south-bank). Each plot had two photo-electronic erosion pins (PEEPs) placed at 1/3 of the bank height (bottom-bank) and the other at 2/3 of the bank height (top-bank). PEEP daily measurements were compared to daily precipitation and streamflow. The continuously grazed pasture banks had the highest erosion rates. The grass area banks had approximately equal rates of erosion and deposition. The riparian forest buffer banks had high erosion rates during the second year. In the continuously grazed pasture, fluvial entrainment was the dominant erosion process, although minor mass failures also caused erosion. In the riparian forest buffer most erosion was recorded after moderate streamflows removed the bank soil loosened by freeze–thaw cycling. This occurred in late winter/early spring, when trees provide primarily mechanical but not hydraulic reinforcement to stream banks and on the lower part of the banks that have less extensive root networks. Overall, stream bank erosion and deposition in each sub-reach occurred during different time periods and under different processes and conditions. This indicates the need for continuous erosion and deposition measurements along with continuous soil moisture, soil temperature and streamflow measurements to fully comprehend these erosion phenomena.

Erratum to: Effectiveness of Grass Filters in Reducing Phosphorus and Sediment Runoff

One of the reference entries of this article has an error. The first name and the family names of the authors had been interchanged. The reference “Jasen,T., Kevin, T.,Esther, S.,Andrea, K.,&Don, N. (2011).Spring snowmelt impact on phosphorus addition to surface runoff in the Northern Great Plains. Better Crops/Vol. 95, No. 1) should read Jensen, T., Tiessen, K., Salvano, E., Kalischuk, A. & Flaten, D. N. (2011). Spring snowmelt impact on phosphorus addition to surface runoff in the Northern Great Plains. Better Crops, 95, 28-31.). Water Air Soil Pollut (2013) 224:1661 DOI 10.1007/s11270-013-1661-7

Temporal evolution of atrazine, metolachlor, and deethylatrazine concentrations in runoff from grass filter strips in a four-season study

<h3>BACKGROUND:</h3> There has not been a detailed description of expiratory reserve volume (ERV) during slow expiration with glottis open in infralateral decubitus position (ELTGOL, for Expiration Lente Totale Glotte Ouverte en infraLatéral) and its reproducibility. The aim of this study was to determine ERV during ELTGOL and to evaluate ERV intra-observer and inter-observer reliability. <h3>METHODS:</h3> In this prospective study, subjects were 30–70 y of age with chronic lung disease. ELTGOL (an active-passive or active physiotherapy technique) was applied in random order by 3 observers: 2 trained physiotherapists (PT 1 and PT 2) and the subject him/herself. Two ELTGOL compressions (A and B) were applied by PT 1, PT 2, and the subject. <h3>RESULTS:</h3> Thirty-two subjects were evaluated with moderate lung obstruction, FEV₁: 47.7 ± 15.4, and ERV: 61.7 ± 29.4. The mean value of ERV for PT 1 was 51.4 ± 24.8%; for PT 2, it was 54.3 ± 31.8%; and for the subject, it was 53.5 ± 26.2% (<i>P</i> = .49). Considering the mean value of ERV, the ELTGOL mobilized more than 80% of ERV. There was good reliability intra-PT: PT 1, intraclass correlation coefficient (ICC) 0.85 (0.70–0.93), <i>P</i> &lt; .0001; PT 2, ICC 0.90 (0.80–0.95), <i>P</i> &lt; .0001, and inter-PT (ICC 0.86 [95% CI 0.71–0.93], <i>P</i> &lt; .001). The Bland-Altman plot with mean bias and limits of agreement for ERV of PT 1 and PT 2 was −3.3 (−42.7 to 35.9). <h3>CONCLUSIONS:</h3> ELTGOL mobilized more than 80% of ERV in subjects with moderate airway obstruction; there is no difference in ERV exhaled during the technique applied by a physiotherapist or by the subject. ELTGOL is a reproducible technique, determined by inter- and intra-observer testing.