The world’s population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.

/pdf/streams-in-the-urban-landscape-mt89v53ix5.pdf

Streams in the Urban Landscape

/pdf/responses-of-woody-plants-to-flooding-and-salinity-4f68qmbyey.pdf

Responses of woody plants to flooding and salinity

http://www.vliz.be/imisdocs/publications/242609.pdf

Seawater intrusion processes, investigation and management: Recent advances and future challenges

Analysis and evaluation of pumping test data

To quantify and model the natural ground water recharge process, six sites located in the midwest and eastern United States where previous water balance observations had been made were compared to computerized techniques to estimate: (1) base flow and (2) ground water recharge. Results from an existing automated digital filter technique for separating baseflow from daily streamflow records were compared to baseflow estimates made in the six water balance studies. Previous validation of automated baseflow separation techniques consisted only of comparisons with manual techniques. In this study, the automated digital filter technique was found to compare well with measured field estimates yielding a monthly coefficient of determination of 0.86. The recharge algorithm developed in this study is an automated derivation of the Rorabaugh hydrograph recession curve displacement method that utilizes daily streamflow. Comparison of annual recharge from field water balance measurements to those computed with the automated recession curve displacement method had coefficients of determination of 0.76 and predictive efficiencies of 71 percent. Monthly estimates showed more variation and are not advocated for use with this method. These techniques appear to be fast, reproducible methods for estimating baseflow and annual recharge and should be useful in regional modeling efforts and as a quick check on mass balance techniques for shallow water table aquifers.

Automated methods for estimating baseflow and ground water recharge from streamflow records

The building of the Silk Road economic belt is an exciting prospect that may bring immense economic benefits to Eurasian countries. However, intensive human activities to be induced by it may double the water crisis in central Asia, deteriorate the vulnerable environment, and accelerate energy consumption in this area. To build a new and sustainable Silk Road economic belt, advancing scientific research, reinforcing international collaboration and enhancing education are necessary steps. With careful planning, sound research, good data and the support from governments and the people, the Silk Road economic belt can be developed in an environmentally sustainable manner that is a credit to all involved.

Building a new and sustainable “Silk Road economic belt”

Deeply weathered crystalline rock forms important aquifers for public water supply throughout low-latitude regions of Africa, South America, and Asia, but these aquifers have considerable heterogeneity and produce low well yields. Aquifers occur in the bedrock and overlying weathered mantle and are the products of geomorphic activity of meteoric water, principally deep weathering and stripping. The fundamental relationship between the hydrogeology and geomorphology of these terrains has, however, remained unresolved. This study demonstrates the ability of a recently developed tectono-geomorphic model of landscape evolution in Uganda to explain the hydrogeological characteristics of two basins, as determined using a combination of textural analysis, slug tests, packer tests, and pumping tests. The geopetal imprint of long-term deep weathering and erosional unloading is identified in the vertical heterogeneity of the fractured-bedrock and weathered-mantle aquifers; horizontal heterogeneity is lithologically controlled. The two units form an integrated aquifer system in which the more transmissive (5–20 m2/d) and porous weathered mantle provides storage to underlying bedrock fractures (transmissivity, T, ≈1 m2/d). The thickness and extent of the more productive weathered-mantle aquifer are functions of contemporary geomorphic processes. The utility of the tectono-geomorphic model, applicable to deeply weathered environments, is that it coherently describes the basin-scale hydrogeological characteristics of these complex terrains.

A tectono-geomorphic model of the hydrogeology of deeply weathered crystalline rock: Evidence from Uganda

Every year, roads and highways in Metropolitan Toronto receive more than 100,000 tonnes (t) of NaCl road de-icing chemicals. While much of this salt is flushed from the region every winter season by overland flow, a proportion will enter the sub-surface and eventually discharge to urban streams as baseflow. To determine annual retention rates of de-icing salts in an urban watershed, a chloride mass balance has been applied to the Highland Creek basin, a typical urban catchment in eastern Metropolitan Toronto. The catchment has an area of 104 km 2 and groundwater recharge is estimated to be 162 mm per year. Chloride in put to the catchment was determined from municipal records. These show that the catchment receives approximately 10,000 t of chloride annually, predominantly in the form of NaCl de-icing chemicals which are applied to road, highways and parking lots during the winter months. Chloride output was estimated from stream flow and electrical conductivity measurements recorded at 15-minute intervals over a two-year period.
			
			The balance reveals that only 45% of the salt applied to the catchment is being removed annually and that the remainder is entering temporary storage in shallow sub-surface waters. If present rates of salt application are maintained, it is predicted that average steady-state chloride concentrations in ground waters discharging as springs in the basin will reach an unacceptable 426 ± 50 mg·L -1 possibly within a 20-year time frame. The value of 426 mg·L -1 represents a three-fold increase over present average baseflow concentrations, and is nearly twice the drinking water quality objective of 250 mg·L -1 maximum acceptable concentration.

/pdf/groundwater-contamination-due-to-road-de-icing-chemicals-4ttlpdrkr1.pdf

Groundwater Contamination Due To Road De-icing Chemicals — Salt Balance Implications

Groundwater chloride response in the Highland Creek watershed due to road salt application: A re-assessment after 20 years

Groundwater vulnerability assessments provide a measure of the sensitivity of groundwater quality to an imposed contaminant load and are globally recognized as an essential element of all aquifer management and protection plans. In this paper, the vulnerability of groundwaters underlying the Yinchuan Plain of Northwest China is determined using OREADIC, a GIS-based assessment tool that incorporates the key characteristics of the universally popular DRASTIC approach to vulnerability assessment but has been modified to consider important additional hydrogeological factors that are specific to the region. The results show that areas of high vulnerability are distributed mainly around Qingtongxia City, Wuzhong City, Lingwu City, and Yongning County and are associated with high rates of aquifer recharge, shallow depths to the water table, and highly permeable aquifer materials. The presence of elevated NO
 3
 −
 in the high vulnerability areas endorses the OREADIC approach. The vulnerability maps developed in this study have become valuable tools for environmental planning in the region and will be used for predictive management of the groundwater resource.

Ken W. F. Howard

Papers

Building a new and sustainable “Silk Road economic belt”

A tectono-geomorphic model of the hydrogeology of deeply weathered crystalline rock: Evidence from Uganda

Groundwater Contamination Due To Road De-icing Chemicals — Salt Balance Implications

Groundwater chloride response in the Highland Creek watershed due to road salt application: A re-assessment after 20 years

Assessment of groundwater vulnerability in the Yinchuan Plain, Northwest China using OREADIC