Agricultural Basin Research Articles

Ephemeral stream sensor design using state loggers

Abstract. Ephemeral streamflow events have the potential to transport sediment and pollutants downstream, which, in predominently agricultural basins, is especially problematic. Despite the importance of ephemeral streamflow, the duration and timing of the events are characteristics that are rarely measured. Ephemeral streamflow sensors have been created in the past with varying degrees of success and this paper presents a solution which minimizes previous shortcomings in other designs. The design and setup of the sensor network in two agricultural basins, as well as considerations for data processing are explored in this paper with regard to monitoring ephemeral streamflow at high spatial and temporal resolutions.

Effect of Aquatic Vegetation on the Persistence of Cypermethrin Toxicity in Water

Soybean production in Argentina comprises 15 million ha. Cypermethrin is the main insecticide applied amounting 150 g of active ingredient per hectare, thus representing roughly 2.3 thousand tons yearly released to the environment. Toxicity pulses have been observed in small streams draining agricultural basins, most of them sustaining macrophyte growth. Cypermethrin concentrations and its toxicity to the amphipod Hyalella curvispina was compared following an addition to laboratory mesocosms with and without a vegetation cover of the floating macrophyte Lemna sp. Both concentrations and toxicity decreased faster in the treatments covered with Lemna. Fast adsorption of the hydrophobic pesticide to the roots and fronds of Lemna was suggested.

Water and nutrient balances in a large tile-drained agricultural catchment: a distributed modeling study

Abstract. This paper presents the development and implementation of a distributed model of coupled water nutrient processes, based on the representative elementary watershed (REW) approach, to the Upper Sangamon River Basin, a large, tile-drained agricultural basin located in central Illinois, mid-west of USA. Comparison of model predictions with the observed hydrological and biogeochemical data, as well as regional estimates from literature studies, shows that the model is capable of capturing the dynamics of water, sediment and nutrient cycles reasonably well. The model is then used as a tool to gain insights into the physical and chemical processes underlying the inter- and intra-annual variability of water and nutrient balances. Model predictions show that about 80% of annual runoff is contributed by tile drainage, while the remainder comes from surface runoff (mainly saturation excess flow) and subsurface runoff. It is also found that, at the annual scale nitrogen storage in the soil is depleted during wet years, and is supplemented during dry years. This carryover of nitrogen storage from dry year to wet year is mainly caused by the lateral loading of nitrate. Phosphorus storage, on the other hand, is not affected much by wet/dry conditions simply because the leaching of it is very minor compared to the other mechanisms taking phosphorous out of the basin, such as crop harvest. The analysis then turned to the movement of nitrate with runoff. Model results suggested that nitrate loading from hillslope into the channel is preferentially carried by tile drainage. Once in the stream it is then subject to in-stream denitrification, the significant spatio-temporal variability of which can be related to the variation of the hydrologic and hydraulic conditions across the river network.

Phytoestrogens and Mycotoxins in Iowa Streams: An Examination of Underinvestigated Compounds in Agricultural Basins

This study provides the first broad-scale investigation on the spatial and temporal occurrence of phytoestrogens and mycotoxins in streams in the United States. Fifteen stream sites across Iowa were sampled five times throughout the 2008 growing season to capture a range of climatic and crop-growth conditions. Basin size upstream from sampling sites ranged from 7 km2 to > 836,000 km2. Atrazine (herbicide) also was measured in all samples as a frame-of-reference agriculturally derived contaminant. Target compounds were frequently detected in stream samples: atrazine (100%), formononetin (80%), equol (45%), deoxynivalenol (43%), daidzein (32%), biochanin A (23%), zearalenone (13%), and genistein (11%). The nearly ubiquitous detection of formononetin (isoflavone) suggests a widespread agricultural source, as one would expect with the intense row crop and livestock production present across Iowa. Conversely, the less spatially widespread detections of deoxynivalenol (mycotoxin) suggest a more variable source due to the required combination of proper host and proper temperature and moisture conditions necessary to promote Fusarium spp. infections. Although atrazine concentrations commonly exceeded 100 ng L(-1) (42/75 measurements), only deoxynivalenol (6/56 measurements) had concentrations that occasionally exceeded this level. Temporal patterns in concentrations varied substantially between atrazine, formononetin, and deoxynivalenol, as one would expect for contaminants with different source inputs and processes of formation and degradation. The greatest phytoestrogen and mycotoxin concentrations were observed during spring snowmelt conditions. Phytoestrogens and mycotoxins were detected at all sampling sites regardless of basin size. The ecotoxicological effects from long-term, low-level exposures to phytoestrogens and mycotoxins or complex chemicals mixtures including these compounds that commonly rake place in surface water are poorly understood and have yet to be systematically investigated in environmental studies.

Efficiency of controlled drainage and subirrigation in reducing nitrogen losses from agricultural fields

In northeast Italy, a regimen of controlled drainage in winter and subirrigation in summer was tested as a strategy for continuous water table management with the benefits of optimizing water use and reducing unnecessary drainage and nitrogen losses from agricultural fields. To study the feasibility and performance of water table management, an experimental facility was set up in 1996 to reproduce a hypothetical 6-ha agricultural basin with different land drainage systems existing in the region. Four treatments were compared: open ditches with free drainage and no irrigation (O), open ditches with controlled drainage and subirrigation (O-CI), subsurface corrugated drains with free drainage and no irrigation (S), subsurface corrugated drains with controlled drainage and subirrigation (S-CI). As typically in the region free drainage ditches were spaced 30 m apart, and subsurface corrugated drains were spaced 8 m apart. Data were collected from 1997 to 2003 on water table depth, drained volume, nitrate-nitrogen concentration in the drainage water, and nitrate-nitrogen concentration in the groundwater at various depths up to 3 m. Subsurface corrugated drains with free drainage (S) gave the highest measured drainage volume of the four regimes, discharging, on average, more than 50% of annual rainfall, the second-highest concentration of nitrate-nitrogen in the drainage water, and the highest nitrate-nitrogen losses at 236 k ha−1. Open ditches with free drainage (O) showed 18% drainage return of rainfall, relatively low concentration of nitrate-nitrogen in the drainage water, the highest nitrate-nitrogen concentration in the shallow groundwater, and 51 kg ha−1 nitrate-nitrogen losses. Both treatments with controlled drainage and subirrigation (O-CI and S-CI) showed annual rainfall drainage of approximately 10%. O-CI showed the lowest nitrate-nitrogen concentration in the drainage water, and the lowest nitrogen losses (15 kg ha−1). S-CI showed the highest nitrate-nitrogen concentration in the drainage water, and 70 kg ha−1 nitrate-nitrogen losses. Reduced drained volumes resulted from the combined effects of reduced peak flow and reduced number of days with drainage. A linear relationship between daily cumulative nitrate-nitrogen losses and daily cumulative drainage volumes was found, with slopes of 0.16, 0.12, 0.07, and 0.04 kg ha−1 of nitrate-nitrogen lost per mm of drained water in S-CI, S, O, and O-CI respectively. These data suggest that controlled drainage and subirrigation can be applied at farm scale in northeast Italy, with advantages for water conservation.

Estimating groundwater withdrawals in areas of intensive agricultural pumping in central Spain

▶ Application of the water table fluctuation method to estimate groundwater pumping. ▶ Geostatistical analysis of the water table map. ▶ Results cross-checked against official pumping data. Measuring groundwater extractions is central to adequate groundwater management in agricultural basins. Groundwater pumping records are often subject to considerable uncertainties, particularly in the case of arid and semiarid settings where irrigation is the most important water use. In most cases this is due to the difficulties involved in locating and monitoring all wells. We describe the estimation of groundwater pumping by coupling the water table fluctuation method with the groundwater balance equation. This is demonstrated through its application to the Mancha Occidental aquifer, Spain, an area subject to intensive pumping for irrigation since the early 1970s. A sensitivity analysis is conducted to evaluate the effect of relevant hydrogeological parameters, namely specific yield, as well as the most appropriate theoretical semivariogram, to calculate yearly storage variations within the system. Results are validated in the light of official pumping estimates.

Diffuse Source Particulate-Matter Pollution Modeling in a Semi-Urbanized Agricultural Basin in Japan Using Process-Based WEP and an Erosion-Transport Model

The present study aimed at further improving the process-based WEP (Water and Energy Processes) hydrologic model, by coupling a soil erosion-transport model to introduce particle-bound pollutant component. The WEP model, initially developed for the extensive analysis of water and energy budgets at catchment scale, was later enhanced by incorporating material transport component (nitrogen and phosphorus; N and P), targeting integrated river basin management and decision support. The model involved a discharge-based process to simulate both N and P, and was validated using data in Yata River Basin, Japan, considering land use, plant acreage, fertilizer loading, plant nutrient uptake and crop harvest in respective administrative units. Although the model could adequately reproduce the dissolved N (DN) component as per the measured river N concentrations at selected observation points, particulate N and P (PN, PP), and dissolved P (DP) components were not satisfactorily simulated. In the present study, an attempt was made to incorporate PN and PP transport as soil absorbed constituents, by introducing a process-based sediment erosion, transport, deposition and associated pollutant load simulation procedures. The present modeling results indicate that PN and PP loads were better correlated with suspended solids (SS) in the stream and the model forecasting capabilities are noticeably enhanced, as verified based on the results obtained for simulation years 2001-2002 using pre-collected data (SS, PN and PP), signifying major pathways of nutrient losses in the basin.

Prediction of Groundwater Contamination with Multivariate Regression and Probabilistic Capture Zones

Probabilistic capture zones are combined with a regression model and used as buffer zones around wells for Tobit regression analysis to predict contaminant concentration of groundwater in an agricultural region. A backward transport equation, which is a mathematical model based on the physical processes of solute transport, is used to delineate probabilistic capture zones. The probabilistic capture zone defines the area where contaminant discharge can have a direct influence, with pertinent probability, on the quality of groundwater pumped from a well. Tobit regression analysis is used to find the relationship between independent regression variables and a dependent variable, which is contaminant concentration in this study. The capture zone and the regression are combined into a model, and its applicability for prediction of nitrate concentration is tested in a small agricultural basin in Chuncheon, Korea, which is occupied mainly by vegetation fields, orchards, and small barns. Three cases of Model 1, Model 2, and Model 3 are compared in which buffer zones are circles, capture zones with probability over 0.1, and capture zones divided into sections with different probabilities, respectively. The resulting regression model describes nitrate concentration in terms of selected independent variables. When the concentrations are calculated with the model, the best fit with the observed concentrations was in Model 3. This result supports the applicability of the method proposed in this study to prediction of contaminant concentration of groundwater.

Fertilizer standards for controlling groundwater nitrate pollution from agriculture: El Salobral-Los Llanos case study, Spain

Summary Although the legislation on groundwater quality targets pollutant concentration, the effects of measures on non-point source pollution control are often evaluated in terms of their emission reduction potential at the source, not on their capacity of reducing the pollutant concentration in groundwater. This paper applies a hydro-economic modelling framework to an aquifer, El Salobral-Los Llanos aquifer (Mancha Oriental, Spain), where nitrate concentrations higher than those allowed by the EU Water Framework Directive and Groundwater Directive are locally found due to the intense fertilizer use in irrigated crops. The approach allows defining the economically optimal allocation of spatially variable fertilizer standards in agricultural basins using a hydro-economic model that links the fertilizer application with groundwater nitrate concentration at different control sites while maximizing net economic benefits. The methodology incorporates results from agronomic simulations, groundwater flow and transport into a management framework that yields the fertilizer allocation that maximizes benefits in agriculture while meeting the environmental standards. The cost of applying fertilizer standards was estimated as the difference between the private net revenues from actual application and the scenarios generated considering the application of the standards. Furthermore, the cost of applying fertilizer standards was compared with the cost of taxing nitrogen fertilizers in order to reduce the fertilizer use to a level that the nitrate concentration in groundwater was below the limit. The results show the required reduction of fertilizer application in the different crop areas depending on its location with regards to the control sites, crop types and soil–plant conditions, groundwater flow and transport processes, time horizon for meeting the standards, and the cost of implementing such a policy (as forgone benefits). According to the results, a high fertilizer price would be required to reduce nitrate concentrations in groundwater below the standard of 50 mg/l. In this particular case, it is more cost-efficient to apply standards to fertilizer use than taxes, although the instrument of fertilizer standards is more difficult to implement and control.

Factors which shape the load of water ecosystems with mineral nitrogen runoffs in rural areas

Abstract The present study of factors which affect the load of water ecosystems with mineral nitrogen compounds (N-NH4 and N-NO3) was conducted in the Olsztyn Lake District and covered the time period from 1992 to 1999. Three capture basins were investigated: agricultural drained with a drain network, agricultural drained with a drainage ditch, and agricultural-forested drained with scattered drains and ditches. It was found that the concentration and load of mineral forms of nitrogen in waters running off from rural areas were closely dependent on meteorological conditions, the kind of artificial drainage system in use, and the type of land use in the catchment area. In waters carried away through the drainage systems, average annual concentrations of N-NH4 ranged from 0.16 mg dm-3 (the agricultural capture basin drained with ditches) to 1.09 mg dm-3 (the agricultural catchment drained with a network of drains); the amounts of N-NO3 ranged from 0.29 mg dm-3 (the agricultural-forested catchment) to 8.06 mg dm-3 (the agricultural catchment drained with a network of drains). It was also observed that a larger share of arable lands in the land use structure in a given catchment caused an increase in the load of N-NO3 determined in drained waters. In addition, it was confirmed that the amounts of mineral nitrogen carried away with drained waters annually varied from 12.78 kg N (6.7 kg N on average) per 1 ha of an agriculturally used catchment, of which N-NO3 was a dominant form (12.23 kg).

Riverine water transformation during retention in small lowland reservoirs

Abstract Six small dam reservoirs in northeastern Poland, with different hydrologic and catchment characteristics were selected for research from March to October (2001-2003). There was a significant correlation between DOC and TP in the reservoirs and the water retention time (WRT). The highest values of electrical conductivity (EC) were recorded in reservoirs with an agricultural basin. In almost all reservoirs a statistically significant decrease of EC, compared to inflowing waters, was noted. Nitrates were substantially reduced in afforested catchment reservoirs. The highest TP concentration was recorded in a newly flooded reservoir. In reservoirs with long retention time, phosphorus sedimentation takes place more intensively. This caused phosphorus reduction in outflowing waters.

Quality of Groundwater in the Shallow Aquifers of a Paddy Dominated Agricultural River Basin, Kerala, India

Groundwater is an essential and vital component of our life support system. The groundwater resources are being utilized for drinking, irrigation and industrial purposes. There is growing concern on deterioration of groundwater quality due to geogenic and anthropogenic activities. Groundwater, being a fragile must be carefully managed to maintain its purity within standard limits. So, quality assessment and management are to be carried out hand-in-hand to have a pollution free environment and for a sustainable use. In order to assess the quality for consumption by human beings and for use in agriculture, the groundwater from the shallow aquifers (dug well) in the Palakkad and Chittur taluks of Bharathapuzha river basin - a paddy dominated agricultural basin (order=8 th ; L= 209 Km; Area = 6186 Km 2 ), Kerala, India, has been selected. The water samples (n=

Application of isotopic and geochemical tools for the evaluation of nitrogen cycling in an agricultural basin, the Fucino Plain, Central Italy

Geochemical and isotope data collected in the agricultural area of Fucino Plain, Central Italy provided information about the relationship between the nitrate cycle and agricultural practices and seasonal changes in hydrology, in particular concerning the interaction between groundwater and surface water. The nitrate cycle of the alluvial aquifer of the Plain has been summarized in a seasonal-dependent conceptual model, where the shallow alluvial aquifer plays a fundamental role contributing to contamination of irrigation channels during periods of no manure application. Based on isotopic fingerprinting, chemical characterization and agricultural practices, the main nitrate source involved in the nitrate cycle in the study area is manure that is applied during the fall and winter periods. A nitrogen contribution from the deep alluvial–lacustrine aquifer was also documented in this study. The isotope data also showed the occurrence of denitrification occurring in nitrate pools in the shallow aquifer, which is characterized by low-permeability layers. The nitrate pool in the shallow aquifer is related to infiltration after the application of manure. The isotope and concentration data showed that the increase of nitrate in the irrigation channels under non-runoff conditions is controlled by seepage from the shallow aquifer. The cycle ends with a new application of manure, generating considerable increases of “fresh” nitrate concentration in the channels. The historical trend of decreasing water table conditions and increasing nitrate content in the shallow aquifer threatens the deep aquifer, used for drinking purposes, since heavy pumping can induce the transport of nitrate from the shallow aquifer toward the capture zone of the deep wells.

The Effects of Season and Agriculture on Nitrous Oxide Production in Headwater Streams

Streams and rivers are a globally significant source of nitrous oxide (N(2)O), a potent greenhouse gas. However, there remains much uncertainty in the magnitude of N(2)O emissions from these sources, partly due to an incomplete understanding of the factors that control microbial N(2)O production in lotic sediments. During 2004-2005 we measured sediment N(2)O production in 12 headwater streams across an agricultural land use gradient. Stream water nitrate (NO(3)(-)) concentrations were positively related to the proportion of agricultural land use in the basin and frequently exceeded 20 mg N L(-1) in the stream draining the most agricultural basin. Stream sediments were nearly always a net source of N(2)O, and production rates were positively related to stream water NO(3)(-) concentrations and sediment carbon content. There were no seasonal patterns in N(2)O production rates during 2004, but stream water NO(3)(-) and N(2)O production both peaked during the winter of 2005. The spike in NO(3)(-) concentrations likely resulted from winter rain and snowmelt that flushed NO(3)(-) from the soils following a dry summer and fall. In turn, the elevated stream water NO(3)(-) concentrations stimulated in-stream N(2)O production rates. Overall, we were only able to explain 29% of the variation in N(2)O production rates on a log scale. The unexplained variation may be due to differences in the fraction of denitrified NO(3)(-) that is converted to N(2)O among the study sites, or that our measures of substrate availability in the water column were not reflective of substrate availability in the porewater used by denitrifiers.

The effect of decreasing fertilization on agricultural nitrogen leaching: a model study

In Finland, the use of agricultural nitrogen (N) fertilizers has decreased since the beginning of the 1990’s but there is not yet any clear response in observed water quality in the monitored agricultural catchments and river basins. It is therefore important to analyse how the reduction in N fertilization affects N leaching at the root zone scale. In this study the nutrient leaching model ICECREAM was used to demonstrate the effects of climatic conditions and decreased N input on N leaching. Ten years (1991–2000) of climatic input data from five stations located in different parts of the country were used as input to simulate nitrate N (NO3-N) leaching from barley cultivation with i) constant N fertilization (Baseline simulation, 90 kg N ha–1) and ii) decreasing N fertilization (N Reduction Scenario simulation: annual linear decrease from 110 to 90 kg N ha–1). The annual and regional variation of simulated N leaching was considerable in both the Baseline and N Reduction Scenario simulations. In the Baseline simulation the average annual NO3-N leaching was 24% of the N fertilization amount. From 1991 to 2000, the annual N leaching decreased close to Baseline leaching values in the N Reduction Scenario simulations, but the decrease was not linear due to high variability in N losses caused by changes in annual weather conditions. The model results indicate that it is possible to achieve a reduction in root zone N leaching by adjusting the fertilizer levels.;

Epilithic diatom assemblages and their relationship to environmental characteristics in an agricultural watershed (Guadiana River, SW Spain)

Abstract Large-scale patterns of benthic diatom assemblages were analyzed in an agricultural basin, the Guadiana River. The distribution patterns of epilithic diatom assemblages were analyzed at different spatial scales: the whole watershed, the upper calcareous subcatchment and the mid-lower siliceous subcatchment. At the whole watershed scale, two major ecological gradients were revealed. The first one summarized the diatom distribution throughout a nutrient concentration gradient, while the second gradient was related to the geological structure of the watershed. Variance partitioning allowed the effects of the different sets of environmental parameters related to every CCA gradient to be separated. Analyzing the subcatchment gradients with partial CCA allowed us to define specific key factors that affect diatom species composition. Although water chemistry consistently played the most important role in structuring diatom assemblages in the Guadiana, spatial factors such as altitude or geographic location also explained some variation in diatom distribution.

Runoff formation in a tile-drained agricultural basin of the Harz Mountain Foreland, Northern Germany

By taking two different tile-drained agricultural basins with porous aquifers in the lowlands of northern Germany as examples, it is demonstrated with an integrated study approach that this type of basin responds similarly to an input as forested mountainous basins with dominant fractured rock aquifers in the central European highlands do. The control mechanism is local rise of pressure heads of aquifers starting with the infiltration process. It is shown that drain laterals in agricultural basins function like fractures and faults in those hard rock basins, i.e. as efficient drain pipe lines. This effect is amplified by hydraulic pressure transmission in the course of single input events, and additionally verified here with the help of artificial and environmental tracers. As a result stream flow is predominantly generated by exfiltrating groundwater. For this process drain laterals constitute fast hydraulic short cuts in the sense of preferential flow paths preferably in case that groundwater tables reach up to the level tile-drain networks.

Estimating Groundwater Withdrawal in Poorly Gauged Agricultural Basins

A method is presented for estimating the annual groundwater withdrawal based on water balance resulting from surface and groundwater hydrological considerations. The unknown groundwater losses of the aquifer are estimated from the groundwater level fluctuations, the specific yield and the groundwater withdrawal prior to the installation of the irrigation network. The meteorological and hydrometric data are used in the Sacramento hydrological conceptual model for the estimation of the stored groundwater volume, via minimization of the difference between the simulated and measured stream discharge. Following the installation of the network due to poorly kept field records, an initial estimation of the groundwater withdrawal is made based on the fluctuations of the groundwater level, the specific yield, and the annual precipitation. The monthly stored groundwater volume is verified against the volume obtained during the recharge of the basin (November–April). The difference between the groundwater volume and the measured discharge of the basin (May–October) is in agreement with the initial estimation of the groundwater withdrawal. This method is applied successfully in an agricultural basin on the island of Crete, Greece and its novelty lies in the fact that it can be used in basins where groundwater withdrawal is not known or data is incomplete.

Comparative Study of Transport Processes of Nitrogen, Phosphorus, and Herbicides to Streams in Five Agricultural Basins, USA

Agricultural chemical transport to surface water and the linkage to other hydrological compartments, principally ground water, was investigated at five watersheds in semiarid to humid climatic settings. Chemical transport was affected by storm water runoff, soil drainage, irrigation, and how streams were linked to shallow ground water systems. Irrigation practices and timing of chemical use greatly affected nutrient and pesticide transport in the semiarid basins. Irrigation with imported water tended to increase ground water and chemical transport, whereas the use of locally pumped irrigation water may eliminate connections between streams and ground water, resulting in lower annual loads. Drainage pathways in humid environments are important because the loads may be transported in tile drains, or through varying combinations of ground water discharge, and overland flow. In most cases, overland flow contributed the greatest loads, but a significant portion of the annual load of nitrate and some pesticide degradates can be transported under base-flow conditions. The highest basin yields for nitrate were measured in a semiarid irrigated system that used imported water and in a stream dominated by tile drainage in a humid environment. Pesticide loads, as a percent of actual use (LAPU), showed the effects of climate and geohydrologic conditions. The LAPU values in the semiarid study basin in Washington were generally low because most of the load was transported in ground water discharge to the stream. When herbicides are applied during the rainy season in a semiarid setting, such as simazine in the California basin, LAPU values are similar to those in the Midwest basins.

Animal movement in dynamic landscapes: interaction between behavioural strategies and resource distributions

Most ecological and evolutionary processes are thought to critically depend on dispersal and individual movement but there is little empirical information on the movement strategies used by animals to find resources. In particular, it is unclear whether behavioural variation exists at all scales, or whether behavioural decisions are primarily made at small spatial scales and thus broad-scale patterns of movement simply reflect underlying resource distributions. We evaluated animal movement responses to variable resource distributions using the grey teal (Anas gracilis) in agricultural and desert landscapes in Australia as a model system. Birds in the two landscapes differed in the fractal dimension of their movement paths, with teal in the desert landscape moving less tortuously overall than their counterparts in the agricultural landscape. However, the most striking result was the high levels of individual variability in movement strategies, with different animals exhibiting different responses to the same resources. Teal in the agricultural basin moved with both high and low tortuosity, while teal in the desert basin primarily moved using low levels of tortuosity. These results call into question the idea that broad-scale movement patterns simply reflect underlying resource distributions, and suggest that movement responses in some animals may be behaviourally complex regardless of the spatial scale over which movement occurs.