The Dallas-Monmouth area, located in the west-central Willamette Valley, Oregon, consists of Tertiary marine and volcanic bedrock units which are locally overlain by alluvium. The occurrence of groundwater with high salinities has forced many rural residents to use public water supplies. Lithologic descriptions from driller's logs, geochemical (INAA), and x-ray diffraction analyses were used to determine alluvial facies distribution, geochemical and clay mineral distinctions among the units, and possible sediment sources. Driller's log, chemical and isotopic analysis, and specific conductance information from wells and springs were used to study the hydrogeologic characteristics of the aquifers and determine the distribution, characteristics, controlling factors, and origin of the problem groundwaters. Three lithologic units are recognized within the alluvium on the basis of grain-size: 1) a lower fine-grained unit; 2) a coarse-grained unit; and 3) an upper fine-grained unit. As indicated by geochemical data, probable sediment sources include: 1) Cascade Range for the recent river alluvium; 2) Columbia Basin plutonic or metamorphic rocks for the upper fine-grained older alluvium; and 3) Siletz River Volcanics from the west for the coarse-grained sediment of the older alluvium. The Spencer Formation (Ts) is geochemically distinct from the Yamhill Formation (Ty) and the undifferentiated Eocene-Oligocene sedimentary rock (Toe) with higher Th, Rb, K, and La and lower Fe, Sc, and Co concentrations. The clay mineralogy of the Ty is predominantly smectite (86%) while the Ts contains a more varied clay suite (kaolinite, 39%; smectite, 53%; and illite 8%). The Ty and Toe are geochemically similar, but are separated stratigraphically by the Ts. The Siletz River Volcanics is distinct from the marine sedimentary units with higher Fe, Na, Co, Cr and Sc concentrations. The Ty and Toe are geochemically similar to volcanic-arc derived sediments while the Ts is similar to more chemically-evolved continental crust material. Wells that encounter groundwater with high salinities (TDS>300 mg/1): 1) obtain water from the marine sedimentary bedrock units or the older alluvium; 2) are completed within zones of relatively low permeability (specific capacities ~5 gpm/ft); and 3) are located in relatively low-lying topographic settings. The poor quality waters occurring under these conditions may be due to the occurrence of mineralized, regional flow system waters. Aquifers of low permeability are less likely to be flushed with recent meteoric water, whereas upland areas and areas with little low permeability overburden are likely zones of active recharge and flushing with fresh, meteoric water. The most saline waters sampled have average isotopic values (6D = -6.7 ° / 00 and 60 = -1.7 ° / 00 ) very near to SMOW, while the other waters sampled have isotopic signatures indicative of a local meteoric origin. The Br/Cl ratios of most (10 of 14) of the waters sampled are within 20% of seawater. A marine connate origin is proposed for these waters with varying amounts of dilution with meteoric waters and water-rock interaction. The problem waters can be classified into three chemically distinct groups: 1) CaC12 waters, with Ca as the dominant cation; 2) NaCl waters with Na as the dominant cation; and 3) Na-Ca-Cl waters with nearly equal Na and Ca concentrations. The NaCl and CaC12 waters may have similar marine connate origins, but have undergone different evolutionary histories. The Na-Ca-Cl waters may represent a mixing of the NaCl and CaC12 waters.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A Ãrea deste estudo de hidrogeologia abrange a Bacia do BanabuiÃ, trecho entre Quixeramobim e BanabuiÃ, e està localizada Ãs margens dos rios Quixeramobim e BanabuiÃ. à necessÃrio para os usuÃrios e gestores conhecer os aspectos qualitativos e quantitativos das Ãguas usadas e a interaÃÃo entre as Ãguas dos rios Quixeramobim e Banabuià com os aquÃferos aluvionares. O objetivo deste estudo foi aprofundar os conhecimentos sobre a hidrogeologia dos aluviÃes em relaÃÃo Ãs reservas, qualidade e hidrodinÃmica das Ãguas. Para isto, realizou-se o cadastro de poÃos, monitoramento das variaÃÃes dos nÃveis estÃticos, levantamento planialtimÃtrico, levantamento geofÃsico por resistividade, medidas de parÃmetros fÃsico-quÃmicos, biolÃgicos, metais pesados, anÃlises isotÃpicas (18O e D) nas Ãguas da chuva, dos poÃos, dos rios Banabuià e Quixeramobim, e do aÃude BanabuiÃ. A estimativa das reservas dos aquÃferos aluvionares tambÃm foi realizada. No tratamento e interpretaÃÃo dos dados usou-se o diagrama de Piper, diagrama USSL, Ato e Resist, para interpretaÃÃo das SEVs, programa Surfer 8.0 para simulaÃÃo do fluxo subterrÃneo, e padrÃes de potabilidade da portaria N 2914/2011 do MinistÃrio da SaÃde. Verificou-se que o fluxo subterrÃneo dirige-se na mesma direÃÃo dos rios Quixeramobim e BanabuiÃ, ou seja, em direÃÃo ao Leste. O aquÃfero aluvionar apresenta uma espessura mÃdia da ordem de 7,08 m. A recarga dos aluviÃes no trecho entre Quixeramobim e Banabuià foi de 6,09x106 m3/ano e a reserva permanente à de aproximadamente 34,8x106 m3. Os principais problemas para o consumo humano das Ãguas (superficiais e subterrÃneas) sÃo os coliformes totais, o elemento ferro, a elevada salinidade, o nitrato, o manganÃs e o alumÃnio, estes se encontram com valores acima do permitido pela Portaria n 2914 do MinistÃrio da SaÃde. Portanto, estas Ãguas sà podem ser consumidas apÃs o devido tratamento. Para o uso na irrigaÃÃo, as Ãguas superficiais e dos aluviÃes podem ser utilizadas sem muitos problemas, jà a Ãgua do domÃnio hidrogeolÃgico cristalino, requer uma prÃtica de irrigaÃÃo controlada. A reta meteÃrica local dos isÃtopos estÃveis para o perÃodo estudado foi muito semelhante à GMWL. Os aquÃferos aluvionares recebem alimentaÃÃo pelos rios Quixeramobim e BanabuiÃ. As Ãguas dos poÃos do domÃnio hidrogeolÃgico cristalino sofreram recarga apenas por Ãguas meteÃricas. As Ãguas dos poÃos do aquÃfero aluvionar sugerem que sofreram evaporaÃÃo durante a recarga. Finalmente, ocorre uma estratificaÃÃo (tÃrmica e quÃmica) no perÃodo chuvoso e uma desestratificaÃÃo no perÃodo de estiagem. / The area of this hydrogeological study covers the Banabuià Basin, in the stretch between Quixeramobim and BanabuiÃ, and is located on the banks of rivers Quixeramobim and BanabuiÃ. It is necessary for users and water managers to be aware of the qualitative and quantitative aspects of the water and the interaction between the rivers Quixeramobim and Banabuià and the alluvial aquifers. For these reasons, we sought to deepen the knowledge about the hydrogeology of the alluvial deposits with respect to reserves, hydrodynamics and water quality. Methods included a data bank of wells, monitoring of changes in static levels, a planialtimetric survey, a geophysical survey by electric resistivity, measurements of physico-chemical and biological parameters, heavy metals, stable isotope analyses (18O and D) in rain, waters from wells, rivers Banabuià and Quixeramobim, and Banabuià dam. An estimation of reserves of alluvial aquifers was also made. In the treatment and interpretation of the data Piper and USSL diagrams were used as well as, Ato and Resist for interpretation of VES, program Surfer 8.0 for simulation of groundwater flow; potability standards of Portaria NÂ. 2914/2011 of the Ministry of Health were used to judge water quality. Results indicate that the groundwater flow has in the same direction of rivers Quixeramobim and BanabuiÃ, ie eastward. The alluvial aquifer has an average thickness of approximately 7.1 m. The recharge to the alluvium in the stretch between Quixeramobim and Banabuià was of 6.09 x106 m3/year and permanent reserve is of approximately 34.8 x106 m3. The main problems for human consumption of the waters (surface and groundwater) are total coliforms, the element iron, high salinity, nitrate, manganese and aluminum; these present values higher than permitted by Portaria N 2914. Therefore, these waters can only be consumed after proper treatment. In irrigation, surface water and alluvium can be used without many problems; however, waters from the crystalline domain require a practice of controlled irrigation. The stable isotope local meteoric water line for the period studied showed a slope very similar to the GMWL. The alluvial aquifers receive recharge from rivers Quixeramobim and BanabuiÃ. Wells in the crystalline bedrock receive recharge by rainwater. The waters of the alluvial aquifer wells suggest that they suffered evaporation while recharging. Finally, there is a slight stratification in Banabuià dam (thermal and chemical) in the rainy season that disappears in the dry season.

Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C₃ Prosopis veleruina (mesquite) trees, whereas the burned plots are open C₄-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant -available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C₃ shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C₄ grasses to C₃ shrubs in surface soil layers. δ¹³C(SOM) values indicate that the Holocene and Late Pleistocene were dominated by C₄ grasslands, and the pre-Late Pleistocene vegetation was a C₄-grass savanna with abundant C₃ plants.

Aquifers in the arid alluvial basins of the southwestern U.S. are recharged predominantly by infiltration from streams within the basins and by water entering along the margins of the basins from surrounding mountains (mountain -front recharge). The Tucson Basin of Southeastern Arizona is such a basin. The Santa Catalina Mountains form the northern boundary of this basin and receive more than twice as much precipitation (about 70 cm/yr) as the basin does (about 30 cm/yr). In this study environmental isotopes were employed to investigate the migration of precipitation basinward through joints and fractures. Water samples were obtained from springs in the Santa Catalina Mountains. Stable isotopes and thermonuclear bomb-produced tritium enabled qualitative characterizations of flow paths and flow velocities. Stable isotopic measurements fail to display a direct altitude effect. Tritium values indicate that although a few springs discharge pre-bomb water, most springs discharge waters from the 1960's or later.

From the Proceedings of the 1972 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 5-6, 1972, Prescott, Arizona / An average of 6 to 13 streamflows from intense summer convective storms occurs annually in the walnut gulch experimental station, 58 square miles in southeastern Arizona. Flows last generally less than 6 hours, and the channels are dry 99 percent of the time. The limiting factors imposed by the geology and geomorphology of the channel to transmission losses of a 6 square mile channel in the station are described. The Precambrian to quaternary geology is outlined, and geomorphology of the channels are described. Volume, porosity and specific yield of alluvium were determined. There is 106 acre-feet of alluvium with a mean specific yield of 28 percent, and a maximum water absorbing capacity of 29 acre-feet or 7 acre-feet per mile of reach. Channel slope is insensitive to changes in geological material beneath it or to changes in flow regime. Channel cross section is highly sensitive to geology and flow regime. Transmission losses were highly correlated to volume of inflow.

From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona / All groundwater in fort valley is presently found in perched aquifers. The regional water table in the area is estimated to lie at a depth of approximately 1750 feet. Groundwater reservoirs are perched on impermeable clay zones located at the base of alluvial units. Groundwater is also found in highly fractured volcanic zones overlaying impermeable clay zones. Perched aquifers also occur in interflow zones above either impermeable clays or unfractured volcanics. Groundwater in fort valley is the result of infiltration or runoff and from precipitation. This recharge water infiltrates the alluvium or fractured volcanic rocks until an impermeable zone is reached where it becomes perched groundwater. Greatest well yields come from these recharge aquifers; their reliability is largely dependent on precipitation and runoff. Most wells in the fort valley area supply adequate amounts of water for domestic use.

From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona / Water yield studies and flood control surveys often necessitate estimating transmission losses from ungaged watersheds. There is an immediate need for an economical method that provides the required accuracy. Analysis of relations between stream order, drainage area, and volume of channel alluvium existing in the various orders is one means of estimating loss potential. Data needed for the stream order survey are taken from aerial photos. Stream order is analyzed using stereophoto maps. Stream lengths taken from the maps are combined with average channel width and depth data (determined by prior surveys) to estimate volumes of alluvium involved. The volume of channel alluvium in a drainage network is directly related to the stream order number of its channels. Thus, a volume of alluvium within a drainage network (with a known transmission loss potential) may be estimated by knowing the order of each length of channel and the drainage areas involved. In analyzing drainage areas of 56-mi² or less, 70 to 75 percent of the total drainage network length is contained within first and second order channels; yet, these constitute less than 10 percent of the total transmission loss potential of the areas. Analysis of stream order and drainage area versus volume of alluvium relations allows preliminary estimates of transmission loss potential to be made for ungaged areas.