Walter Rast

Trends in eutrophication research and control

Eutrophication is the natural ageing process of lakes. It is characterized by a geologically slow shift from in-lake biological production driven by allochthonous (external to the water body) loading of nutrients, to production driven by autochthonous (in-lake) processes. This shift typically is accompanied by changes in species and biotic community composition, as an aquatic ecosystem is ultimately transformed into a terrestrial biome. However, this typically slow process can be greatly accelerated by human intervention in the natural biogeochemical cycling of nutrients within a watershed; the resulting cultural eutrophication can create conditions inimical to the continued use of the water body for humandriven economic purposes. Excessive algal and rooted plant growth, degraded water quality, extensive deoxygenation of the bottom water layers and increased fish biomass accompanied by decreased harvest quality, are some features of this process. Following the Second World War, concern with cultural eutrophication achieved an intensity that spurred a significant research effort, culminating in the identification of phosphorus as the single most significant, and controllable, element involved in driving the eutrophication process. During the late 1960s and throughout the 1970s, much effort was devoted to reducing phosphorus in wastewater effluents, primarily in the developed countries of the temperate zone. These efforts generally resulted in the control of eutrophication in these countries, albeit with varying degrees of success. The present effort in the temperate zone, comprising mostly developed nations, has now shifted to the control of diffuse sources of a broader spectrum of contaminants that impact human water use. In the developing countries of the inter-tropical zone, however, rapidly expanding populations, a growing industrial economy and extensive urbanization have only recently reached an intensity at which cultural eutrophication can no longer be ignored. Further, initial attempts at applying temperate zone control measures in this region have been largely unsuccessful. Modification of the temperate zone eutrophication paradigm will be needed, especially to address the differing climatic and hydrological conditions, if cultural eutrophication is to be contained in this region, where eutrophication-related diseases continue to be a primary cause of human distress.

A Systems Approach to Understanding the Evolution of the Agro-Social-Ecological System of the Upper Rio Grande-San Luis Valley, Colorado

Understanding the complex dynamics of social-ecological systems (SES) is difficult because rigorous methodologies and methods for this purpose are lacking. Multi-scale (temporal and geographical) linkages and pathways can mask feedbacks. Thus, understanding SES requires multi-dimensional analyses. This study presents a potential methodology and method for multi-dimensional analyses of a SES in the Upper Rio Grande-San Luis Valley (URG-SLV), Colorado. A driver identification process identified 5 major drivers in the URG-SLV, including stream flow, climate, agriculture, and endogenous and exogenous policy. Several of these drivers possessed more than one longitude. Data for these drivers begins as early as 1852 and extends to 2007. Changes in driver longitudes (long-term datasets within a single driver; maximum, minimum and mean annual temperature comprise climate longitudes) were detected via change point analysis, occurring at several transitional points. Linkages were defined using known relationships between drivers (e.g., stream flow and water rights). Cross-scale relationships between the URG-SLV and downstream users through policy changes and climate also presented a temporal cross-scale linkage. Using the relationships and cross-scale linkages, a historical evolution of the system was constructed throughout the 150-plus years of record to illustrate the effects of changes in drivers and cross-scale linkages in the system.

Hydrologic-Economic Analysis of Best Management Practices for Sediment Control in the Santa Fe Watershed, New Mexico

The Santa Fe River Watershed in Santa Fe County, New Mexico was identified as one of the top five high risk nonpoint source pollution areas out in the Rio Grande Basin. This watershed was selected to demonstrate the use of hydrologic modeling as a powerful tool for assessing the impacts of land management practices on erosion and sediment control at the watershed level. A method based on the Hydrologic Simulation Program-Fortran was used to address the local nonpoint sediment pollution concerns. The model was modified to reflect predicted future land uses related to expected urban expansion in the watershed. Six scenarios were created and the costs and benefits of each were weighed. The total estimated costs ranged from under

The World Lake Vision and ecohydrology: case study from Wisconsin, USA

1 million to over

Semiquantitative Analysis of Water Appropriations and Allocations in the Upper Rio Grande Basin, Colorado

66 million. Total average annual sediment yields at the watershed outlet ranged from 3,441 to 4,111 tonnes/year, depending on management practices employed. These results indicate the magnitude of expected sediment reductions under various management strategies. Additionally, they provide an indication of the magnitude of expected sediment reductions in the Santa Fe Watershed and the estimated cost of each management practice.

Control of eutrophication of lakes and reservoirs.

Abstract The World Lake Vision represents a firm global foundation for lake management across national and cultural boundaries. It provides a set of sustainable use and protection goals for our global water resources. Based on seven principles, the World Lake Vision emphasizes the need for a balance between people, and requires the participation of citizens and policy makers in lake management planning efforts. The recently-completed lake and stream restoration project at Upper Kelly Lake, City of New Berlin, Waukesha County, and Village of Hales Corners, Milwaukee County, Wisconsin (USA) forms a case study illustrating the successful application of these seven principles. Upper Kelly Lake is a small drainage lake in an urbanized location, with a stream inlet that has been historically channelized. Through the efforts of the Kelly Lakes Association, Inc., in addition to local and state governments, lake protection and lake management grants were acquired to fund the stream and wetland restoration project described in this case study.

Nutrient Loading Estimates for Lakes

AbstractA semiquantitative analysis was used to assess the impacts of water rights appropriations and allocations in the Upper Rio Grande (URG) Basin, in Colorado. The study also explores the causes and effects of the changes on collateral elements in the URG agriculture system, namely the San Luis Valley (SLV) in Colorado. Population increases, after the acquisition of the territory from 1854 to 1900, were the major cause of increased acquisitions of surface water rights. By 1912 surface waters were nearly 100% appropriated. The population continued to increase until 1930 after which it remained stable. Water users began making large increases in the number of appropriations of groundwater around 1925, with the majority of increases starting around 1935. As a result, moratoriums were placed on well development in the 1970s and 80s. Individual spikes in water rights acquisitions of surface and groundwater were associated with periodic droughts and high crop prices. Change point time series analysis identi...