Ag-Drainage Wells and Groundwater Quality

Iowa agriculture benefits from two important natural resources, the rich soils that blanket the landscape and sufficient precipitation, in most years, to produce large crop yields. While precipitation is essential to farmers, many of Iowa\u27s soils, especially in the northcentral part of the state, are poorly drained and at times contain excess water that can hinder field operations or ruin crops. In these areas, farm fields are often artificially drained by buried tile lines leading to ditches or to streams. Another, but less common, method is the agricultural drainage well, a shaft which funnels excess water directly underground. The upper parts of these wells are fed by tile lines; other wells also are designed to receive surface runoff. Ag-drainage wells are usually 5 to 10 inches in diameter and are cased from the land surface to the top of bedrock. They vary in depth from 30 to over 300 feet. There is currently no accurate count of these wells in Iowa, but most estimates suggest 600 to 700 with the greatest concentration in Humboldt, Pocahontas and Floyd counties

Nitrogen and phosphorus budgets for Iowa and Iowa watersheds

https://ir.uiowa.edu/igs_tis/1046/thumbnail.jp

Potential for Geologic Sequestration of CO2 in Iowa

https://ir.uiowa.edu/igs_tis/1056/thumbnail.jp

Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient

In arthropod community ecology, species richness studies tend to be prioritised over those investigating patterns of abundance. Consequently, the biotic and abiotic drivers of arboreal arthropod abundance are still relatively poorly known. In this cross-continental study, we employ a theoretical framework in order to examine patterns of covariance among herbivorous and predatory arthropod guilds. Leaf-chewing and leaf-mining herbivores, and predatory ants and spiders, were censused on > 1000 trees in nine 0.1 ha forest plots. After controlling for tree size and season, we found no negative pairwise correlations between guild abundances per plot, suggestive of weak signals of both inter-guild competition and top-down regulation of herbivores by predators. Inter-guild interaction strengths did not vary with mean annual temperature, thus opposing the hypothesis that biotic interactions intensify towards the equator. We find evidence for the bottom-up limitation of arthropod abundances via resources and abiotic factors, rather than for competition and predation.publishedVersio

Results from the big spring basin water quality monitoring and demonstration projects

Abstract Agricultural practices, hydrology, and water quality of the 267-km 2 Big Spring groundwater drainage basin in Clayton County, Iowa, have been monitored since 1981. Land use is agricultural; nitrate-nitrogen (-N) and herbicides are the resulting contaminants in groundwater and surface water. Ordovician Galena Group carbonate rocks comprise the main aquifer in the basin. Recharge to this karstic aquifer is by infiltration, augmented by sinkhole-captured runoff. Groundwater is discharged at Big Spring, where quantity and quality of the discharge are monitored. Monitoring has shown a threefold increase in groundwater nitrate-N concentrations from the 1960s to the early 1980s. The nitrate-N discharged from the basin typically is equivalent to over one-third of the nitrogen fertilizer applied, with larger losses during wetter years. Atrazine is present in groundwater all year; however, contaminant concentrations in the groundwater respond directly to recharge events, and unique chemical signatures of infiltration versus runoff recharge are detectable in the discharge from Big Spring. Education and demonstration efforts have reduced nitrogen fertilizer application rates by one-third since 1981. Relating declines in nitrate and pesticide concentrations to inputs of nitrogen fertilizer and pesticides at Big Spring is problematic. Annual recharge has varied five-fold during monitoring, overshadowing any waterquality improvements resulting from incrementally decreased inputs. Résumé Les pratiques culturales, l'hydrologie et la qualité de l'eau du bassin d'alimentation de la source de Big Spring, étendu de 267 km 2 , située dans le comté de Clayton (Iowa, Etats-Unis) ont été suivis depuis 1981. Ce territoire est utilisé par l'agriculture; l'azote des nitrates (N) et les pesticides sont les contaminants des eaux souterraines et des eaux de surface qui en résultent. Les roches carbonatées ordoviciennes du groupe Galena constituent le principal aquifère du bassin. Cet aquifère karstique est rechargé par l'infiltration à laquelle s'ajoute le ruissellement de surface drainé par des pertes. L'eau souterraine ressort à Big Spring, dont le débit et la qualité des eaux sont contrôlés. Ce contrôle a montré que les concentrations en azote des nitrates des eaux souterraines ont triplé entre les années soixante et les années quatre-vingt. L'azote des nitrates issu du bassin équivaut au tiers de l'azote des engrais appliqués, avec des pertes plus importantes au cours des années plus humides. L'atrazine est présente dans les eaux souterraines tout au long de l'année; cependant, les concentrations en contaminants des eaux souterraines répondent directement aux épisodes de recharge et les signatures chimiques uniques de l'infiltration par rapport à la recharge par le ruissellement sont détectables à l'exutoire de Big Spring. Les Resumen Se han controlado las prácticas agrícolas, hidrología y calidad del agua de la cuenca de Big Spring (267 km 2 ), en el Condado de Clayton, desde el año 1981. Los usos del suelo son eminentemente agrícolas, hecho que acarrea la presencia de nitratos y herbicidas en las aguas subterráneas y superficiales. El acuífero principal de la cuenca está formado por rocas carbonatadas del Grupo de Galenas del Ordovícico. La recarga a este acuí-fero kárstico se produce por infiltración, que se ve aumentada por la existencia de dolinas. Las aguas subterrá-neas descargan al Big Spring, en el que existe una red de control de su cantidad y calidad. Los registros históricos muestran que las concentraciones de nitratos se han multiplicado por tres entre 1960 Results from the Big Spring basin water quality monitoring and demonstration projects, Iowa, USA Robert D. Rowden · Huaibao Liu · Robert D. Libra y comienzos de los 80. El nitrato drenado en la cuenca equivale a un tercio del nitrógeno aplicado como fertilizante, si bien se produce más lixiviados en los años hú-medos. Se ha detectado atracina de forma regular durante el año en las aguas subterráneas, aunque las concentraciones responden directamente a los episodios de recarga; en la descarga del Big Spring, se aprecia la correlación química existente entre la infiltración y las aguas de escorrentía superficial. La educación y los esfuerzos de divulgación han reducido en un tercio la carga de fertilizantes nitrogenados desde 1981. Sin embargo, es complicado relacionar las reducciones en el uso de nitratos y pesticidas con las concentraciones de dichos compuestos en el Big Spring. La recarga anual ha variado en un factor de cinco durante el período registrado, difuminando las mejoras de calidad de las aguas obtenidas gracias a la disminución de las dosis de contaminantes

Agricultural drainage wells in Iowa : hydrogeologic settings and water-quality implications

https://ir.uiowa.edu/igs_tis/1023/thumbnail.jp

Groundwater monitoring in the Big Spring Basin, 1994-1995 : a summary review

https://ir.uiowa.edu/igs_tis/1036/thumbnail.jp

Groundwater and surface water monitoring in the Big Spring basin 1996-1999 : a summary review

https://ir.uiowa.edu/igs_tis/1043/thumbnail.jp

Groundwater and surface-water monitoring in the Bugenhagen sub-basin, 1986-1995 : a summary review

https://ir.uiowa.edu/igs_tis/1040/thumbnail.jp

Shallow groundwater and surface water monitoring of the Silver Creek sub-basin within the Big Spring basin, 1986-1995 : a summary review

https://ir.uiowa.edu/igs_tis/1037/thumbnail.jp