Farm Dams Research Articles

Fencing farm dams to exclude livestock halves methane emissions and improves water quality.

Agricultural practices have created tens of millions of small artificial water bodies (“farm dams” or “agricultural ponds”) to provide water for domestic livestock worldwide. Among freshwater ecosystems, farm dams have some of the highest greenhouse gas (GHG) emissions per m2 due to fertilizer and manure run‐off boosting methane production—an extremely potent GHG. However, management strategies to mitigate the substantial emissions from millions of farm dams remain unexplored. We tested the hypothesis that installing fences to exclude livestock could reduce nutrients, improve water quality, and lower aquatic GHG emissions. We established a large‐scale experiment spanning 400 km across south‐eastern Australia where we compared unfenced (N = 33) and fenced farm dams (N = 31) within 17 livestock farms. Fenced farm dams recorded 32% less dissolved nitrogen, 39% less dissolved phosphorus, 22% more dissolved oxygen, and produced 56% less diffusive methane emissions than unfenced dams. We found no effect of farm dam management on diffusive carbon dioxide emissions and on the organic carbon in the soil. Dissolved oxygen was the most important variable explaining changes in carbon fluxes across dams, whereby doubling dissolved oxygen from 5 to 10 mg L−1 led to a 74% decrease in methane fluxes, a 124% decrease in carbon dioxide fluxes, and a 96% decrease in CO2‐eq (CH4 + CO2) fluxes. Dams with very high dissolved oxygen (>10 mg L−1) showed a switch from positive to negative CO2‐eq. (CO2 + CH4) fluxes (i.e., negative radiative balance), indicating a positive contribution to reduce atmospheric warming. Our results demonstrate that simple management actions can dramatically improve water quality and decrease methane emissions while contributing to more productive and sustainable farming.

Australian farm dams are becoming less reliable water sources under climate change

Worldwide food production is under ever-increasing demand. Meanwhile, climate change is disrupting rainfall and evaporation patterns, making agriculture freshwater supplies more uncertain. IPCC models predict an increased variability in rainfall and temperature over most of the globe under climate change. Yet, the effects of climate variability on water security remain poorly resolved. Here we used satellite images and deep-learning convolutional neural networks to analyse the impacts of annual averages, seasonality, climate anomaly, and temporal autocorrelation (or climate reddening) for rain and temperature on the water levels of >100,000 Australian farm dams across 55 years. We found that the risk of empty farm dams increased with warmer annual temperatures, lower yearly rainfall, stronger seasonality, reduced climate anomalies, and higher temporal autocorrelation. We used this information to develop a predictive model and estimate the likelihood of water limitations in farm dams between 1965 and 2050 using historical data and Coupled Model Intercomparison Project Phase 5 (CMIP5) at two climate change scenarios. Results showed that the frequency of empty water reserves has increased 2.5-fold since 1965 and will continue to increase across most (91%) of Australia. We estimated a 37% decline in rural areas with year-round water supplies between 1965 (457,076 km2) and 2050 (285,998 km2). Our continental-scale assessment documents complex temporal and spatial impacts of climate change on agricultural water security, with ramifications for society, economy, and the environment.

Improved management of farm dams increases vegetation cover, water quality, and macroinvertebrate biodiversity.

In many farming landscapes, aquatic features, such as wetlands, creeks, and dams, provide water for stock and irrigation, while also acting as habitat for a range of plants and animals. Indeed, some species threatened by land‐use change may otherwise be considerably rarer—or even suffer extinction—in the absence of these habitats. Therefore, a critical issue for the maintenance of biodiversity in agricultural landscapes is the extent to which the management of aquatic systems can promote the integration of agricultural production and biodiversity conservation. We completed a cross‐sectional study in southern New South Wales (southeastern Australia) to quantify the efficacy of two concurrently implemented management practices—partial revegetation and control of livestock grazing—aimed at enhancing the vegetation structure, biodiversity value, and water quality of farm dams. We found that excluding livestock for even short periods resulted in increased vegetation cover. Relative to unenhanced dams (such as those that remained unfenced), those that had been enhanced for several years were characterized by reduced levels of turbidity, nutrients, and fecal contamination. Enhanced dams also supported increased richness and abundance of macroinvertebrates. In contrast, unenhanced control dams tended to have high abundance of a few macroinvertebrate taxa. Notably, differences remained between the macroinvertebrate assemblages of enhanced dams and nearby “natural” waterbodies that we monitored as reference sites. While the biodiversity value of semilotic, natural waterbodies in the region cannot be replicated by artificial lentic systems, we consider the extensive system of farm dams in the region to represent a novel ecosystem that may nonetheless support some native macroinvertebrates. Our results show that management interventions such as fencing and grazing control can improve water quality in farm dams, improve vegetation structure around farm dams, and support greater abundance and diversity of aquatic macroinvertebrates.

Remote Sensing and Hydrologic-Hydrodynamic Modeling Integrated Approach for Rainfall-Runoff Simulation in Farm Dam Dominated Basin

Farm dams may exert various pressures on the flow network depending on the position and scale, which may influence the magnitude, timing, and duration of the flow in the basin. Considering the cumulative effects of farm dams is important for understanding their spatial impacts on the rainfall-runoff process. However, a few studies have been able to reckon the temporal and spatial variation in the flow. In this study, we developed an integrated approach based on remote sensing and hydrologic–hydrodynamic modeling to simulate the rainfall-runoff process in a farm dam-dominated basin. Compared with the classical Xinanjiang model (XAJ), the developed coupled hydrological–hydrodynamic model (coupled-XAJ) shows improved performance in the simulation of the no-linear confluence process in terms of flood flow and peak appearance time. It demonstrates that water retention of multiple farm dams is eminent and that the developed model is effective and feasible in farm dam-dominated basins. Furthermore, the integrated approach enables to control and utilize the rain and flood resources with the safety of arm dams guaranteed. This study provides an innovative method for the scientific management of water resources under the influence of human activities and environmental changes.

Habitat element associations in the bird fauna of an Australian farmland landscape

Context The decline of birds in farmland is of global concern. Aims The aim of this paper was to provide a local-scale case study of the bird fauna of temperate inland eastern Australia’s sheep–wheat belt. Methods Relationships between species occurrence and various habitat elements in the landscape were examined in a 342 km2 area of agricultural countryside near Wagga Wagga in southern inland New South Wales, Australia. The pre-agricultural bird fauna of this area was also investigated by collating records from previous studies of nearby larger woodland remnants. Key results The study identified a bird fauna of 115 species compared to 160 species known from nearby woodland remnants. Significant relationships were found with the presence of farm dams, extent of local woodland cover and roadside woodland at the levels of individual species, guilds and total fauna. A small ephemeral wetland also contributed substantially to waterbird diversity. Conclusion Twenty commonly recorded species typical of the farmland matrix and 15 species considered at particular risk of local extinction were identified. At the guild level, frugivore/granivores, small insectivores and hollow-users were found to be associated with remaining woodland elements in the agricultural landscape. Implications Ecologically sustainable management of agricultural areas is essential to avoid further local extinctions. Hollow-using species are expected to be particularly affected by the anticipated widespread loss of trees in the landscape over the next century.

Growth performance of Nile tilapia reared in cages in a farm dam submitted to a feed reduction strategy in a periphyton‐based system

The periphyton-based system is a low-cost and sustainable strategy for small-scale producers who have limited technology and budgets. This study aimed to evaluate the effects of different feed restriction levels (50% and 67%), using periphyton as a natural food source, on the growth performance of Nile tilapia reared under real culture conditions in cages placed in a farm dam. Three treatments were tested: F100—fish fed daily only on feed; F50—fish fed every other day, plus periphyton; and F33—fish fed every two days, plus periphyton. Considering the results of fish growth in F50 and F33 compared with F100 and the low amount of periphyton dry matter, it is reasonable to state that the fish under feed restriction did not take advantage of the periphyton due to its low availability. This low availability of the periphyton is possibly associated with the water N:P ratio and its variation over the experimental period. Therefore, periphyton-based systems are not indicated for conditions with a low N:P ratio or subject to great variations in this ratio.

Increased livestock weight gain from improved water quality in farm dams: A cost-benefit analysis.

Access to water is a critical aspect of livestock production, although the relationship between livestock weight gain and water quality remains poorly understood. Previous work has shown that water quality of poorly managed farm dams can be improved by fencing and constructing hardened watering points to limit stock access to the dam, and revegetation to filter contaminant inflow. Here we use cattle weight gain data from three North American studies to develop a cost-benefit analysis for the renovation of farm dams to improve water quality and, in turn, promote cattle weight gain on farms in south-eastern Australia. Our analysis indicated a strong likelihood of positive results and suggested there may be substantial net economic benefit from renovating dams in poor condition to improve water quality. The average per-farm Benefit-Cost Ratios based on deterministic assumptions was 1.5 for New South Wales (NSW) and 3.0 for Victoria in areas where rainfall exceeds 600mm annually. Our analyses suggested that cattle on farms in NSW and Victoria would need to experience additional weight gain from switching to clean water of at least 6.5% and 1.8% per annum respectively, to break even in present value terms. Monte Carlo simulation based on conservative assumptions indicated that the probability of per-farm benefits exceeding costs was greater than 70%. We recommend localised experiments to assess the impact of improved water quality on livestock weight gain in Australian conditions to confirm these expectations empirically.

Modelling the impact of climate change on the flow of the Eerste River in South Africa

This research investigated the impact of climate change on the Eerste River, which is the primary source of water for the Stellenbosch Municipality and the agricultural sector in the surrounding areas of Stellenbosch Town, South Africa. Climate data projected by 11 Global Circulation Models (GCMs) of the Coupled Model Intercomparison Project - Phase 5 enforced by Representative Concentration Pathways 4.5 and 8.5, was statistically downscaled to reflect the “near” (2022–2057) and “far” (2058–2093) future periods, respectively. The ensemble mean of these GCMs outputs for the near and far future periods was compared to that of the present-day period which was accepted as the period between 1983 and 2018. This was done to determine the climate change signal, which was then transferred onto the observed precipitation and evaporation data of the present-day period. The climate change induced data, as well as land use and water demand analysed data, were then used as input to the Pitman Model, which is the conceptual semi-distributed hydrological model, for the simulation of the impact of climate change on the flow of the Eerste River. The results showed that climate change is expected to increase evaporation between 6% and 15% and, at the same time, causing rainfall to decrease between 2% and 8% in the future periods. This future climate is anticipated to cause a reduction in available water of between 8% and 18%, potentially triggering an increase in irrigation demand of between 12% and 29% in the future periods with a possible failure to meet the municipal water abstractions expected in the far-future period. Therefore, this research suggests increasing the capacity of existing farm dams and the promotion of water demand management practices to curb the potential impact of climate change on the available flow of the Eerste River.

A Continental-Scale Assessment of Density, Size, Distribution and Historical Trends of Farm Dams Using Deep Learning Convolutional Neural Networks

Farm dams are a ubiquitous limnological feature of agricultural landscapes worldwide. While their primary function is to capture and store water, they also have disproportionally large effects on biodiversity and biogeochemical cycling, with important relevance to several Sustainable Development Goals (SDGs). However, the abundance and distribution of farm dams is unknown in most parts of the world. Therefore, we used artificial intelligence and remote sensing data to address this critical global information gap. Specifically, we trained a deep learning convolutional neural network (CNN) on high-definition satellite images to detect farm dams and carry out the first continental-scale assessment on density, distribution and historical trends. We found that in Australia there are 1.765 million farm dams that occupy an area larger than Rhode Island (4678 km2) and store over 20 times more water than Sydney Harbour (10,990 GL). The State of New South Wales recorded the highest number of farm dams (654,983; 37% of the total) and Victoria the highest overall density (1.73 dams km−2). We also estimated that 202,119 farm dams (11.5%) remain omitted from any maps, especially in South Australia, Western Australia and the Northern Territory. Three decades of historical records revealed an ongoing decrease in the construction rate of farm dams, from >3% per annum before 2000, to ~1% after 2000, to <0.05% after 2010—except in the Australian Capital Territory where rates have remained relatively high. We also found systematic trends in construction design: farm dams built in 2015 are on average 50% larger in surface area and contain 66% more water than those built in 1989. To facilitate sharing information on sustainable farm dam management with authorities, scientists, managers and local communities, we developed AusDams.org—a free interactive portal to visualise and generate statistics on the physical, environmental and ecological impacts of farm dams.

Cryptosporidium and Giardia in dam water on sheep farms – An important source of transmission?

Cryptosporidium and Giardia infections can negatively impact livestock health and reduce productivity, and some species and genotypes infecting livestock have zoonotic potential. Infection occurs via the faecal-oral route. Waterborne infections are a recognised source of infection for humans, but the role of livestock drinking water as a source of infection in livestock has not been described. This study aimed to determine whether contaminated drinking water supplies, such as farm dams, are a likely transmission source for Cryptosporidium and Giardia infections for extensively managed sheep. Dam water samples (n = 47) were collected during autumn, winter and spring from 12 farm dams located on six different farms in south west Western Australia, and faecal samples (n = 349) were collected from sheep with access to these dams. All samples were initially screened for Cryptosporidium spp. at the 18S locus and Giardia spp. at the gdh gene using qPCR, and oocyst numbers were determined directly from the qPCR data using DNA standards calibrated by droplet digital PCR. Cryptosporidium-positive sheep faecal samples were typed and subtyped by sequence analysis of 18S and gp60 loci, respectively. Giardia-specific PCR and Sanger sequencing targeting tpi and gdh loci were performed on Giardia- positive sheep faecal samples to characterise Giardia duodenalis assemblages. To identify Cryptosporidium and Giardia spp. in dam water samples, next-generation sequencing analysis of 18S and gdh amplicons were performed, respectively. Two species of Cryptosporidium (Cryptosporidium xiaoi and Cryptospordium ubiquitum (subtype family XIIa)) were detected in 38/345 sheep faecal samples, and in water from 9/12 farm dams during the study period, with C. xiaoi the species most frequently detected in both faeces and dam water overall. Giardia duodenalis assemblages AI, AII and E were detected in 36/348 faecal samples and water from 10/12 farm dams. For dam water samples where oo/cysts were detected by qPCR, Cryptosporidium oocyst concentration ranged from 518–2429 oocysts/L (n = 14), and Giardia cyst concentration ranged from 102 to 1077 cysts/L (n = 17). Cryptosporidium and Giardia with zoonotic potential were detected in farm dam water, including C. ubiquitum, C. hominis, C. parvum, C. cuniculus, C. xiaoi, and G. duodenalis assemblages A, B and E. The findings suggest that dam water can be contaminated with Cryptosporidium species and G. duodenalis assemblages that may infect sheep and with zoonotic potential, and farm dam water may represent one source of transmission for infections.

Antimicrobial resistance screening and profiles: a glimpse from the South African perspective.

According to the Centre for Disease Dynamics Economics and Policy, South Africa represents a paradox of antibiotic management similar to other developing countries, with both overuse and underuse (resulting from lack of access) of antibiotics. In addition, wastewater reuse may contribute towards antibiotic resistance through selective pressure that increases resistance in native bacteria and on clinically relevant bacteria, increasing resistance profiles of the common pathogens. Sediments of surface water bodies and wastewater sludge provide a place where antibiotic resistance genes are transferred to other bacteria. Crop irrigation is thought to be a potential source of exposure to antibiotic-resistant bacteria through the transfer from the water or sludge into crops. The objectives of this study were to examine the antibiotic-resistance profiles of Escherishia coli from three agricultural locations in the Western Cape, South Africa. Using a classical microbiology culture approach, the resistance profiles of E. coli species isolated from river water and sediments, farm dams and their sediments and a passive algal wastewater treatment ponds and sediment used for crop irrigation were assessed for resistance to 13 commonly used antibiotics. Randomly selected E. coli isolates from the sediment and water were tested for resistance. 100% of E. coli isolates were resistant to sulphamethoxazole, highlighting its relevance in the South African context. In river water and farm dam samples, only the E. coli isolated from sediment were found to be resistant to fluoroquinolone or fluorifenicol. In the wastewater treatment ponds, the resistance profiles of E. coli isolated from sediments differed from those isolated from effluent, with 90% of the effluent isolates being resistant to ampicillin. Isolates from the sediment were less resistant (40%) to ampicillin, whereas all the isolates from the pond water and sediment samples were resistant to sulphamethoxazole. These results illustrate the importance of developing a better understanding of antibiotic resistance in agriculture and wastewater scenarios to ensure remedial measures take place where the greatest benefit can be realised especially in countries with limited financial and infrastructural resources. Moreover, the potential for passive algal treatment as an effective, feasible alternative for wastewater treatment is highlighted, with comparable resistance profiles and a reducing overall resistance in the sediment samples.

Life on the farm: are zooplankton communities in natural ponds and constructed dams the same?

Constructed waters (e.g. dams and retired quarries) are commonly found to have a different zooplankton composition than are natural waters, and to be more readily invaded by non-indigenous species. Constructed ponds are common on farmland, but zooplankton research in these areas is scarce. Consequently, our aims were to (1) compare zooplankton communities between natural ponds and dams in rural environments and, (2) examine environmental determinants of zooplankton community composition among rural ponds. Thirty-eight ponds on farmland in New Zealand were sampled for zooplankton in winter–spring 2018 and summer 2019. All ponds were eutrophic, and zooplankton taxa typical of such conditions were common in both pond types (e.g. Brachionus, Keratella and Polyarthra species). Zooplankton community composition differed statistically between each type, although we deemed this difference to be ecologically insignificant (one-way ANOSIM, r=0.09, P=0.014). Prevalence of non-indigenous species was low, with 7% of farm dams and 2% of natural ponds being invaded, indicating that farm ponds are not acting as ‘stepping-stones’ for invaders across landscapes. Macrophyte abundance and concentration of humic substances were the dominant environmental variables measured determining zooplankton distribution among ponds.

Interactive effects of land use, grazing and environment on frogs in an agricultural landscape

Improved management of human-modified landscapes must be part of global efforts to combat biodiversity loss. We aimed to identify which land management types and environmental factors influenced the use of grazing landscapes by frogs. We surveyed frog assemblages in remnant vegetation, four different paddock types (pasture, linear planting, coarse woody debris addition and fence), and two grazing regimes (continuous and rotational). Frogs were surveyed using pitfall and funnel traps in twelve grazing farms in south-eastern Australia.We found that grazed agricultural landscapes provide important habitats for a variety of species of frogs and that frog assemblages were influenced by both farm management type and environmental variables, and their interactions. Total frog abundance increased with proximity to water more strongly in remnants compared to paddocks. This difference in response may be due to different traits and behaviours of frogs in remnants compared to frogs in open paddocks.Rare frog species richness and abundance of a common species (Limnodynastes tasmaniensis) increased with taller ground cover in remnants but no such relationship occurred in paddocks. Different types of predation risk in remnants compared to paddocks may result in greater ground cover shelter requirements in remnants, as vegetation structure can strongly influence predation.Total frog species richness increased more rapidly with higher rainfall in continuously grazed versus rotationally grazed farms. Higher rainfall was associated with taller ground cover. Continuously grazed farms had shorter average ground cover than rotationally grazed farms and the increased ground cover height associated with more rain may bring ground cover to a height better able to provide shelter and reduce desiccation risk for frogs.Our study highlights the importance of both land management practices and environmental conditions and their interaction in shaping frog assemblages. Improved frog biodiversity conservation may be achieved in grazing landscapes by retaining patches of remnant vegetation, maintaining water bodies such as farm dams, and maintaining tall ground cover within vegetation remnants.

Hydrological impact of a reservoir network in the upper Gan River Basin, China

AbstractA few relatively large reservoirs, hundreds of small reservoirs, and numerous farm dams were built in the upper Gan River Basin, China. The operation of such a reservoir network can serve as a significant source of variability in the local hydrological regime and should be included in research to better understand the interaction between multiple hydrological processes and watershed management. In this study, a reservoir network module that included reservoirs of multiple sizes was developed and fully integrated into the coupled land surface and distributed hydrologic model system (CLHMS), for a detailed description of the hydrological impact of a reservoir network. A generalized release scheme was employed to determine the outflow of both large and small reservoirs. The integrated model was then evaluated against observations and reanalysis data, which indicate that the model can reasonably reconstruct the reservoir operation, streamflow, and other hydrological variables. Results quantitatively demonstrate that a reservoir network can result in an increased streamflow in dry seasons, a decreased streamflow in wet seasons, a generally larger groundwater discharge, higher groundwater level, a slightly damper soil condition, and a larger amount of evapotranspiration at the basin level. With the integrated model, it is feasible to achieve more sustainable watershed planning and management.

Movements of Australian Wood Ducks (Chenonetta jubata) in an agricultural landscape

ABSTRACTWe deployed satellite transmitters to provide the first detailed picture of the movement behaviour of Australian Wood Ducks (Chenonetta jubata) through agricultural landscapes where the availability and spatial arrangement of resources are highly predictable. We measured movement distances and home-range areas of individual Australian Wood Ducks and investigated their site fidelity by comparing the overlap of successive home-range areas on a fortnightly temporal scale. First passage time (FPT) analysis was used to determine the spatial scales at which foraging occurs within home-range areas. We found a peak of movement activity around the periods of dawn and dusk similar to many waterfowl species. The mean overlap of core home-range areas over successive 2 week periods was 89.81% (± 2.38 SD), which demonstrates strong site fidelity. Area-restricted search (ARS) occurred at the scale of individual foraging (ca.100 m), with no clear peaks at larger spatial scales. This finding implies that search effort was expended equally across the combined utilisation distribution of Australian Wood Ducks in this agricultural landscape. Our results support the conclusions of previous studies suggesting that the movement behaviour of Australian Wood Ducks is shaped strongly by the temporal and spatial predictability of their grazing areas and access to water in the form of farm dams.

Managing Cumulative Effects of Farm Dams in Southeastern Australia

AbstractChallenges abound for water managers attempting to address problems that have cumulative effects. This paper discusses some of these challenges and potential solutions through a case study ...

Farm dam siltation and sediment source tracing in the Zeerust - Swartruggens area in the North-West of South Africa

Soil erosion and dam siltation are two serious environmental problems facing farmers in South Africa. The study aimed to assess farmers' perceptions on dam siltation and strategies employed to address it, and to assess the potential of sediment source tracing in a farming area in the north-west region of South Africa. Most of the dams in the study area were severely affected by siltation and the most important strategy used to address the problem was regular mechanical removal of the accumulated sediment. In relation to sediment tracing, lead-210 (210Pb) was found to be a more effective tracer than caesium-137 (137Cs) for distinguishing between surface and subsurface sediment sources. On the other hand, magnetic susceptibility offered better distinction of the sediment sources than magnetic remanence. Mass balance modelling indicated that 100% of the sampled sediment dam 1 originated from surface sources. The results reflect the complexity of sediment mobilisation processes influenced by the nature and spatial distribution of rainfall and runoff connectivity in the catchments.

Farm dam siltation and sediment source tracing in the Zeerust Swartruggens area in the north-west of South Africa

Soil erosion and dam siltation are two serious environmental problems facing farmers in South Africa. The study aimed to assess farmers' perceptions on dam siltation and strategies employed to address it, and to assess the potential of sediment source tracing in a farming area in the north-west region of South Africa. Most of the dams in the study area were severely affected by siltation and the most important strategy used to address the problem was regular mechanical removal of the accumulated sediment. In relation to sediment tracing, lead-210 (210Pb) was found to be a more effective tracer than caesium-137 (137Cs) for distinguishing between surface and subsurface sediment sources. On the other hand, magnetic susceptibility offered better distinction of the sediment sources than magnetic remanence. Mass balance modelling indicated that 100% of the sampled sediment dam 1 originated from surface sources. The results reflect the complexity of sediment mobilisation processes influenced by the nature and spatial distribution of rainfall and runoff connectivity in the catchments.

Hydrocleys nymphoides (Alismataceae) naturalised in New South Wales waterways

Hydrocleys nymphoides (Humb. & Bonpl. ex Willd.) Buchenau (Alismataceae) is a stoloniferous emergent/floating perennial aquatic plant native to the Neotropics. In Australia it is naturalised in Queensland, New South Wales, Victoria and the territory Norfolk Island. The earliest non-cultivated collection in New South Wales was made in November 1957 from Castle Hill in Sydney, and although it involved an infestation in several farm dams it was not considered an established naturalised species in that state. Since then it was reported occurring in a dam at Murwillumbah in 1993 and from 2009 naturalised records have been collected from the Murray River at South Albury, near Coffs Harbour on the north coast, and on the Hacking River at Audley in the Royal National Park, south of Sydney. H. nymphoides, commonly called Water Poppy, is grown as an ornamental and has the potential to escape further as an invasive weed, particularly in disturbed wetlands and waterways. A description with images of H. nymphoides, and notes on distribution and genome size are provided.

Punching above their weight: Large release of greenhouse gases from small agricultural dams.

Freshwater ecosystems play a major role in global carbon cycling through the breakdown of organic material and release of greenhouse gases (GHGs). Carbon dioxide (CO2 ) and methane (CH4 ) emissions from lakes, wetlands, reservoirs and small natural ponds have been well studied, however, the GHG emissions of highly abundant, small-scale (<0.01km2 ) agricultural dams (small stream and run-off impoundments) are still unknown. Here, we measured the diffusive CO2 and CH4 flux of 77 small agricultural dams within south-east Australia. The GHG emissions from these waterbodies, which are currently unaccounted for in GHG inventories, amounted to 11.12±2.59gCO2 -equivalent m2 /day, a value 3.43 times higher than temperate reservoir emissions. Upscaling these results to the entire state of Victoria, Australia, resulted in a farm dam CO2 -equivalent/day emission rate of 4,853 tons, 3.1 times higher than state-wide reservoir emissions in spite of farm dams covering only 0.94 times the comparative area. We also show that CO2 and CH4 emission rates were both significantly positively correlated with dissolved nitrate concentrations, and significantly higher in livestock rearing farm dams when compared to cropping farm dams. The results from this study demonstrate that small agricultural farm dams can be a major source of greenhouse gas emissions, thereby justifying their inclusion in global carbon budgets.