RECOVERY OF “LOST” STORM WATER FROM LOCAL WASH BEDS1

ABSTRACT: Most of the precipitation that falls is unused because it never reaches a stream or recharges an underground supply. This storm water evaporates and is transpired and consumed by plants. Described below are pertinent legal principles and the concept for a small-scale system to capture and store some of this “lost” storm water from the subflow of small gravelly washes that are not part of or connected with a stream system. The subsurface flow is interrupted by an elastomer faced earthen barrier (dam) and stored in a gravel bed. Both the barrier and the gravel storage bed are situated below the surface of the wash bed. If the gravel bed is not underlain by a natural substratum that is relatively impervious, it is either placed on a liner of suitable compacted clay or is underlain with an elastomeric membrane to limit the downward infiltration and loss of the stored water. A system may be used to capture and store sub-flow after surface flow has ceased and during periods of drought; to supply household and irrigation water; to exercise Winters Doctrine rights; and to replace small dams and surface impoundments by underground storage of the captured water to ensure a more reliable and sanitary supply for livestock and wildlife. A system is most effective in desert regions where (or when) both stream and ground water are unavailable; where rainfall is infrequent, but in storms resulting in rapid runoff; and where land surface topography and morphology coincide to form sites that permit the productive use of a system. A system should not be installed without sound legal and hydrological advice. Careful engineering is essential to the safe and proper design of a system, especially its subsurface barrier.     

The “Short Cut” Approach for the Reality of Enhanced Groundwater Contamination

Based on the reality of (a) soil heterogeneity in the vadose zone, (b) enhanced desorption from soil and solubility in water of water insoluble contaminants in the presence of surfactants, and (c) wetting/drying cycles of groundwater recharge (a major cause of fractures formation), a coherent “short-cut” conceptual approach is advanced to account for enhanced groundwater contamination. This is an attempt to close the gap between theory, lab simulations and conventional modelling-based predictions, and observed higher concentrations and more rapid arrival times of contaminants reaching groundwater. Recent data concerning chloride ion and non-ionic surfactants concentrations in aquifers and groundwater wells, combined with previous results concerning the concentrations of tritium, chlorides, metals, organic hydrocarbons and surfactants in the unsaturated and saturated zones of Israel's aquifers, are accounted for in terms of the “short-cut” approach. The contradiction between predictions of groundwater contamination made with conventional, deterministic, homogeneous models and the actual observed behavior of contaminants in soils and aquifers is thus explaind. The “short cut” approach should not be perceived as a better type of model to guide modelling. Rather, it is a proposal for a conceptual change from the realistically invalid, but commonly accepted, conventional “buffer-protective soil/long-term groundwater contamination” to the “short cut” conceptual model to explain the enhanced groundwater contamination actually observed. Although the validity of the proposed approach is strongly supported by the data here presented for the case of Israel (serving as an illustrative case study), selected results and conclusions drawn from studies conducted worldwide suggest its general applicability and usefulness. A major conclusion evolved from the “short-cut” conceptual model is that contemporary groundwater management policies, based on the current perception of groundwater contamination processes and their modelling, may result in an irreversible detrimental effect on the environmental situation in the long run. In any case, prevention, rather than correction/remediation, is strongly recommended as the strategy of choice for rational long-term management of groundwater resources.     

The Arkansas Valley “Super Ditch”— An Analysis of Potential Economic Impacts1

McMahon, Tyler G. and Mark Griffin Smith, 2012. The Arkansas Valley “Super Ditch”— An Analysis of Potential Economic Impacts. Journal of the American Water Resources Association (JAWRA) 00(0):000‐000. 1‐12. DOI: 10.1111/jawr.12005 Abstract: In Colorado’s Arkansas River basin, urban growth and harsh farming conditions have resulted in water transfers from agricultural to urban uses. Several studies have shown that these transfers have significant secondary economic impacts associated with the removal of irrigated land from production. In response, new methods of sharing water are being developed to allow water transfers that benefit both farm and urban economies, compared with previous permanent transfers that negatively impacted surrounding farm communities. One such project currently under development is the Arkansas Valley “Super Ditch,” which is a rotational crop fallowing plan based on long‐term water leasing designed to provide an annual supply of 25,000 acre‐feet of water (31.6 Mm³). This article analyzes the net benefits of implementing the “Super Ditch” for both the farmers and the surrounding community.     

ANALYSIS OF HYDRILLA-INHIBITING FRACTIONS IN NATURAL WATERS: THE CONCEPT OF “FINGERPRINTING” THROUGH LIQUID CHROMATOGRAPHY1

ABSTRACT: High performance liquid chromatography (HPLC) has been used to identify a fraction of aqueous sediment extract from Lake Starvation, Hillsborough County, Florida, that is responsible for inhibition of hydrilla growth. The fraction was separated on a Zorbax? C₁₈ preparative-scale column. The present study examines various lake sediment extracts and river water samples to determine the presence or absence of the inhibitor peak. The biologically active component is absent in certain rivers where hydrilla is prominent, but it is present in extracts of Lake Starvation and White Trout Lake sediments that are known to have hydrilla growth inhibiting properties. The implications of “fingerprinting” natural waters for hydrilla inhibitor through liquid chromatography are considered.     

Delving into the “Institutional Black Box”: Revealing the Attributes of Sustainable Urban Water Management Regimes1

van de Meene, Susan J. and Rebekah R. Brown, 2009. Delving into the “Institutional Black Box”: Revealing the Attributes of Sustainable Urban Water Management Regimes. Journal of the American Water Resources Association (JAWRA) 45(6):1448‐1464. Abstract: This paper is based on the proposition that the transition to sustainable urban water management has been hampered by the lack of insight into attributes of a sustainable urban water regime. Significant progress has been made in developing technical solutions to advance urban water practice, however it is the co‐evolution of the socio‐institutional and technical systems that enable a system‐wide transition. A systematic analysis of 81 empirical studies across a range of practice areas was undertaken to construct a schema of the sustainable urban water regime attributes. Attributes were identified and analyzed using a framework of nested management regime spheres: the administrative and regulatory system, inter‐organizational, intra‐organizational, and human resources spheres. The regime is likely to involve significant stakeholder involvement, collaborative inter‐organizational relationships, flexible and adaptive organizational cultures, and motivated and engaging employees. Comparison of the constructed sustainable and traditional regime attributes reveals that to realize sustainable urban water management in practice a substantial shift in governance is required. This difference emphasizes the critical need for explicitly supported strategies targeted at developing each management regime sphere to further enable change toward sustainable urban water management.