Implications of using On-Farm Flood Flow Capture to recharge groundwater and mitigate flood risks along the Kings River, CA

Two large hydrologic issues face the Kings Basin, severe and chronic overdraft of about 0.16M ac-ft annually, and flood risks along the Kings River and the downstream San Joaquin River. Since 1983, these floods have caused over $1B in damage in today’s dollars. Capturing flood flows of sufficient volume could help address these two pressing issues which are relevant to many regions of the Central Valley and will only be exacerbated with climate change. However, the Kings River has high variability associated with flow magnitudes which suggests that standard engineering approaches and acquisition of sufficient acreage through purchase and easements to capture and recharge flood waters would not be cost effective. An alternative approach investigated in this study, termed On-Farm Flood Flow Capture, involved leveraging large areas of private farmland to capture flood flows for both direct and in lieu recharge. This study investigated the technical and logistical feasibility of best management practices (BMPs) associated with On-Farm Flood Flow Capture. The investigation was conducted near Helm, CA, about 20 miles west of Fresno, CA. The experimental design identified a coordinated plan to determine infiltration rates for different soil series and different crops; develop a water budget for water applied throughout the program and estimate direct and in lieu recharge; provide a preliminary assessment of potential water quality impacts; assess logistical issues associated with implementation; and provide an economic summary of the program. At check locations, we measured average infiltration rates of 4.2 in/d for all fields and noted that infiltration rates decreased asymptotically over time to about 2 – 2.5 in/d. Rates did not differ significantly between the different crops and soils tested, but were found to be about an order of magnitude higher in one field. At a 2.5 in/d infiltration rate, 100 acres are required to infiltrate 10 CFS of captured flood flows. Water quality of applied flood flows from the Kings River had concentrations of COC (constituents of concern; i.e. nitrate, electrical conductivity or EC, phosphate, ammonium, total dissolved solids or TDS) one order of magnitude or more lower than for pumped groundwater at Terranova Ranch and similarly for a broader survey of regional groundwater. Applied flood flows flushed the root zone and upper vadose zone of nitrate and salts, leading to much lower EC and nitrate concentrations to a depth of 8 feet when compared to fields in which more limited flood flows were applied or for which drip irrigation with groundwater was the sole water source. In demonstrating this technology on the farm, approximately 3,100 ac-ft was diverted, primarily from April through mid-July, with about 70% towards in lieu and 30% towards direct recharge. Substantial flood flow volumes were applied to alfalfa, wine grapes and pistachio fields. A subset of those fields, primarily wine grapes and pistachios, were used primarily to demonstrate direct recharge. For those fields about 50 – 75% of water applied was calculated going to direct recharge. Data from the check studies suggests more flood flows could have been applied and infiltrated, effectively driving up the amount of water towards direct recharge. Costs to capture flood flows for in lieu and direct recharge for this project were low compared to recharge costs for other nearby systems and in comparison to irrigating with groundwater. Moreover, the potentially high flood capture capacity of this project suggests significant flood avoidance costs savings to downstream communities along the Kings and San Joaquin Rivers. Our analyses for Terranova Ranch suggest that allocating 25% or more flood flow water towards in lieu recharge and the rest toward direct recharge will result in an economically sustainable recharge approach paid through savings from reduced groundwater pumping. Two important issues need further consideration. First, these practices are likely to leach legacy salts and nitrates from the unsaturated zone into groundwater. We develop a conceptual model of EC movement through the unsaturated zone and estimated through mass balance calculations that approximately 10 kilograms per square meter of salts will be flushed into the groundwater through displacing 12 cubic meters per square meter of unsaturated zone pore water. This flux would increase groundwater salinity but an equivalent amount of water added subsequently is predicted as needed to return to current groundwater salinity levels. All subsequent flood flow capture and recharge is expected to further decrease groundwater salinity levels. Second, the project identified important farm-scale logistical issues including irrigator training; developing cropping plans to integrate farming and recharge activities; upgrading conveyance; and quantifying results. Regional logistical issues also exist related to conveyance, integration with agricultural management, economics, required acreage and Operation and Maintenance (O&M).

Microanálise e geoquímica em testemunhos de corais como elementos de interpretação dos impactos das forçantes naturais e antrópicas sobre a costa do Brasil

Corais pétreos são formadores de recifes. Por secretarem carbonato de cálcio pela base de seus pólipos, esses corais zooxantelados formam um exoesqueleto, composto geralmente por cristais de aragonita. Os padrões de crescimento coralinos variam desde a escala sazonal a centenária e podem ser caracterizados pela medida da taxa de crescimento, a variabilidade dos isótopos estáveis de oxigênio e carbono e pelas razões elementares Sr/Ca, Mg/Ca, U/Ca, Cd/Ca, Ra/Ca (entre outras) em seu esqueleto. Em um contexto global, os recifes cumprem importante papel como sumidouros de carbono atmosférico. Diante das evidências de um oceano mais quente na era moderna, a temperatura da superfície do mar (TSM) tem sido considerada um importante fator de controle da calcificação e crescimento coralino. Geralmente, a calcificação tende a aumentar com a elevação da TSM dentro de uma estreita faixa aceitável para o funcionamento pleno do metabolismo coralino. Neste trabalho, desenvolveu-se uma re-análise das taxas de crescimento de testemunhos de corais amostrados na costa brasileira (Salvador-Ba - Baía de Todos os Santos, Parque Nacional Marinho dos Abrolhos-Ba e Armação dos Búzios-RJ) empregando-se uma combinação de bandas de crescimento (alta e baixa densidades) auxiliado pelo método de luminescência e datação por radioisótopos de U e Th. As diferenças nas cronologias para os dois métodos variou de 1 ano para o caso de Abrolhos até 7,4 anos para Búzios (em seções específicas do testemunho). Foram analisadas variações de calcificação no esqueleto coralino e interpretadas à luz das razões Sr/Ca e U/Ca (ambos próxies da TSM), séries climáticas de AMO e PDO, e pH pelágico oceânico. Identificamos uma diminuição na taxa de calcificação do exoesqueleto no tempo estudado na amostra de Salvador de 0,4 g/cm2, e um aumento em Abrolhos de 0,4 g/cm2 e Búzios 0,3 g/cm2, exceto nos anos de 1950 ao final de 1980 e de 1910 ao final de 1930, respectivamente. Uma microtomografia de raio-X foi empregada para determinar micro-estruturas coralinas, sendo os parâmetros mais relevantes a microporosidade e a anisotropia. Para Abrolhos e Búzios, foi identificado um aumento na porosidade total do exoesqueleto, principalmente no começo de 1940 até o fim da década de 1980 e entre 1890 a 1930 respectivamente. Notou-se forte associação entre a redução do padrão de calcificação com o aumento da porosidade. Os testemunhos da espécie Siderastrea stellata coletados em Abrolhos e Búzios mostraram alta associação das razoes Sr/Ca e U/Ca com a taxa de calcificação, caracterizando uma resposta similar a de outros autores para a Grande Barreira na Austrália (DE'ATH et al., 2009) e para a região central do Mar Vermelho (CANTIN et al., 2010). Em relação as razões Ba/Ca, Salvador e Abrolhos evidenciaram variáveis que contribuíram para este aumento como a forçante de produção de petróleo e aumento populacional (economia), e TSM (oceano). Para Búzios, a TSM (oceano), produção de petróleo, aumento populacional e NDVI (economia). Após os anos de 1990, o impacto dos fatores econômicos, além das variáveis oceânicas respondem mais significativamente o aumento da razão Ba/Ca em todos os sítios quase que concomitantemente na costa brasileira.

Defined etching of carbon-diamond films on silicon using an oxygen plasma with titanium masking

A technique for pattern transfer onto carbon-diamond films deposited by radio-frequency plasma-enhanced chemical vapour deposition is reported. Such a technique involves standard photolithography processes and reactive ion etching by oxygen and is compatible with present day microelectronic technology. The patterns transferred are well defined with very good resolution. © 1992.

Paleoenvironmental records from the Quelccaya ice cap, Peru and preliminary results from the Dunde ice cap, China [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The 1000 year records of particulate deposition (soluble and insoluble), oxygen isotopic ratios, and net accumulation from the Quelccaya ice cap are presented. The net accumulation record from Quelccaya is shown to serve as a reasonable proxy for the water levels in Lake Titicaca. ... The ice core record from the Dunde ice cap offers the potential to reconstruct a very detailed history of environmental conditions on the Tibetan Plateau for the last 3000 years.