A FAST RECURSIVE GIS ALGORITHM FOR COMPUTING STRAHLER STREAM ORDER IN BRAIDED AND NONBRAIDED NETWORKS1

ABSTRACT: Stream ordering is a useful property of every river network, having a wide range of applications. A method for determining stream orders that quickly and easily addresses various network topologies and magnitudes is therefore needed. This paper introduces a general recursive stream ordering framework for vector hydrography. It also presents a linear, O(n), stream ordering procedure for braided river networks, which is a major improvement to the existing quadratic, O(n²), procedure. The discussion includes results and interpretations, and the appendices present procedure pseudocodes and thorough line by line explanations.     

The Analysis of Sustainability Indicators as Socially Constructed Policy Instruments: benefits and challenges of 'interactive research'

Sustainability indicator sets are increasingly being discussed on the policy level as fruitful contributions to the improvement of political decision- making and to the implementation of programs oriented towards the achievement of strategic goals of sustainable development. The vast number of different indicator type tools, their varying contexts of use and their differing objectives indicate that there is no simple answer to what sustainable indicator type tools should look like or could be used for. Instead, more than the final products (e.g. a specific indicators set), the analyses of the discourse on this topic reveal a lot of information. Thus, an innovative research approach is recommended focusing on understanding the production of social meaning and processes of social interaction within political-administrative systems. Firstly, there is a need to identify the development, purpose and use of sustainability indicator sets, which depend on the different interests of policy actors, their relationships and existing governance structures. Secondly, one should identify any reasons for the ineffective use of indicator sets where the goals of sustainability are concerned. The approach of 'interactive research' understood as a research process, in which 'researchers' and 'practitioners' develop knowledge for solving problems in a communicative, reflexive and collaborative way, facilitates this challenging research task. This paper critically examines the approach of interactive research and sheds some light on benefits as well as challenges of it via extracting the lessons learnt in an EU-funded project called 'Promoting Action for Sustainability through Indicators at the Local Level in Europe' (PASTILLE), which applied an interactive research approach.     

EFFECT OF PRICE ON THE RESIDENTIAL DEMAND FOR WATER WITHIN AN AGENCY1

ABSTRACT: This paper develops a model that can be used to forecast the residential elasticity of demand for water within a district. Long-term water conservation programs and revenue and cost decisions hinge crucially on a determination of this elasticity. This study then pools cross-sectional (census) and time series data to generate elasticity forecasts for the Oakland urban area.     

TRENDS IN LEAD CONCENTRATIONS IN MAJOR U.S. RIVERS AND THEIR RELATION TO HISTORICAL CHANGES IN GASOLINE-LEAD CONSUMPTION1

ABSTRACT: Declines in concentrations of dissolved lead occurred at nearly two-thirds of 306 locations on major U.S. rivers from 1974 to 1985. Declines in dissolved lead concentrations are statistically significant (p < 0.10) at approximately one-third of the sampling locations. Statistically significant increases in dissolved lead concentrations occurred at only 6 percent of the sites, but are clustered in the Texas-Gulf and Lower Mississippi regions. Possible explanations for the observed trends in lead concentrations are tested through comparisons with (1) records of lead discharges from major sources including leaded-gasoline consumption and municipal- and industrial-point source discharges, (2) trends in various water-quality constituents such as pH and total alkalinity, and (3) basin characteristics such as drainage area. Statistically significant declines in lead concentrations in streams and gasoline lead (i.e., the largest source of lead at these sites) are highly coincident for the 1979 to 1980 period at most sampling locations. The greatest amount of decline in gasoline lead occurred at sites showing statistically significant downtrends in stream concentrations of lead from 1974 to 1985. No more than 5 percent of the trends in stream lead are influenced by municipal- and industrial-point sources of lead. Factors that affect the transport of dissolved lead, including lead solubility, suspended sediment, and basin characteristics such as drainage basin size, are not significantly related to trends in dissolved lead. Trends in streamflow explain no more than 7 percent of the downtrends in concentrations of lead and may partly explain the frequent increases in lead concentrations in the Texas-Gulf and Lower Mississippi regions.     

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