431 resultados para Watersheds


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Prepared in cooperation with State agricultural experiment stations.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

"Prepared by Science and Education Administration."

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Prepared in cooperation with state agricultural experiment stations.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Final issue consulted: 1972

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We examined the impact of permafrost on dissolved organic matter (DOM) composition in Caribou-Poker Creeks Research Watershed (CPCRW), a watershed underlain with discontinuous permafrost, in interior Alaska. We analyzed long term data from watersheds underlain with varying degrees of permafrost, sampled springs and thermokarsts, used fluorescence spectroscopy, and measured the bioavailabity of dissolved organic carbon (DOC). Permafrost driven patterns in hydrology and vegetation influenced DOM patterns in streams, with the stream draining the high permafrost watershed having higher DOC and dissolved organic nitrogen (DON) concentrations, higher DOC:- DON and greater specific ultraviolet absorbance (SUVA) than the streams draining the low and medium permafrost watersheds. Streams, springs and thermokarsts exhibited a wide range of DOC and DON concentrations (1.5–37.5 mgC/L and 0.14–1.26 mgN/L, respectively), DOC:DON (7.1–42.8) and SUVA (1.5–4.7 L mgC-1 m-1). All sites had a high proportion of humic components, a low proportion of protein components, and a low fluorescence index value (1.3–1.4), generally consistent with terrestrially derivedDOM. Principal component analysis revealed distinct groups in our fluorescence data determined by diagenetic processing and DOM source. The proportion of bioavailable DOC ranged from 2 to 35%, with the proportion of tyrosine- and tryptophan-like fluorophores in the DOM being a major predictor of DOC loss (p\0.05, R2 = 0.99). Our results indicate that the degradation of permafrost in CPCRW will result in a decrease in DOC and DON concentrations, a decline in DOC:DON, and a reduction in SUVA, possibly accompanied by

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Globally, the current state of freshwater resource management is insufficient and impeding the chance at a sustainable future. Human interference within the natural hydrologic cycle is becoming dangerously irreversible and the need to redefine resource managerial approaches is imminent. This research involves the development of a coupled natural-human freshwater resource supply model using a System Dynamics approach. The model was applied to two case studies, Somalia, Africa and the Phoenix Active Management Area in Arizona, USA. It is suggested that System Dynamic modeling would be an invaluable tool for achieving sustainable freshwater resource management in individual watersheds. Through a series of thought experiments, a thorough understanding of the systems’ dynamic behaviors is obtainable for freshwater resource managers and policy-makers to examine various courses of action for alleviating freshwater supply concerns. This thesis reviews the model, its development and an analysis of several thought experiments applied to the case studies.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The Rathbun Land and Water Alliance and partners have undertaken a highly effective approach to water quality protection through the Rathbun Lake Special Project. This approach is achieving a significant reduction in the sediment and phosphorus that impair water quality in Rathbun Lake and its tributaries as a result of the targeted application of best management practices (BMPs) for priority land in the watershed. This project application proposes to assist landowners to apply BMPs that will reduce sediment and phosphorus delivery from priority land in three targeted sub-watersheds as part of the Rathbun Lake Special Project. Features of this project are:(1) use of geographic information system (GIS) analysis to identify priority land that requires BMPs;(2) assistance for landowners to apply BMPs for 1,200 acres that will reduce the annual delivery of sediment by 1,800 tons and phosphorus by 6,000 pounds;(3) evaluation of the benefits from BMP application using GIS analysis and water quality monitoring; and (4) watershed outreach activities that encourage landowners to apply BMPs for priority land to protect water quality.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Carbon and nitrogen loading to streams and rivers contributes to eutrophication as well as greenhouse gas (GHG) production in streams, rivers and estuaries. My dissertation consists of three research chapters, which examine interactions and potential trade-offs between water quality and greenhouse gas production in urban streams of the Chesapeake Bay watershed. My first research project focused on drivers of carbon export and quality in an urbanized river. I found that watershed carbon sources (soils and leaves) contributed more than in-stream production to overall carbon export, but that periods of high in-stream productivity were important over seasonal and daily timescales. My second research chapter examined the influence of urban storm-water and sanitary infrastructure on dissolved and gaseous carbon and nitrogen concentrations in headwater streams. Gases (CO2, CH4, and N2O) were consistently super-saturated throughout the course of a year. N2O concentrations in streams draining septic systems were within the high range of previously published values. Total dissolved nitrogen concentration was positively correlated with CO2 and N2O and negatively correlated with CH4. My third research chapter examined a long-term (15-year) record of GHG emissions from soils in rural forests, urban forest, and urban lawns in Baltimore, MD. CO2, CH4, and N2O emissions showed positive correlations with temperature at each site. Lawns were a net source of CH4 + N2O, whereas forests were net sinks. Gross CO2 fluxes were also highest in lawns, in part due to elevated growing-season temperatures. While land cover influences GHG emissions from soils, the overall role of land cover on this flux is very small (< 0.5%) compared with gases released from anthropogenic sources, according to a recent GHG budget of the Baltimore metropolitan area, where this study took place.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The WorldFish Center has been collaborating with its partners (AWF and WWF) in the Maringa-Lopori-Wamba (MLW) and the Lac Tele-Lac Ntomba (LTL) Landscapes to develop participatory monitoring systems for aquatic ecosystems. This requires rigorous data collection regarding fishing effort and catch, and the establishment of community partnerships; enabling WorldFish Center researchers to understand and counteract the institutional legacies of previous NGO interventions. In the MLW, fisherfolk livelihoods are severely limited due to their extreme isolation from markets and government services. However, fisherfolk have some experience dealing with natural resource conservation or extraction entities as well as humanitarian agencies. Their history has left them slightly skeptical but reasonably willing to collaborate with incoming NGOs. Around Lac Ntomba, fisherfolk have had more extensive interactions with conservation and humanitarian NGOs, but despite their proximity to the Congo River, they appear to have very limited access to distant markets. As past benefits from NGO activities have been captured by local village elites many fishers are highly skeptical and even antagonistic toward NGOs in general, and see little benefits from collaborating with each other or NGOs. Similarly to the MLW and Lac Ntomba, Lac Maï-Ndombe fisherfolk were disillusioned by past NGO activities. However, in this area levels of fish catch are greater than in the other watersheds, and many fishers make regular trips to major markets in Kinshasa, Kikwit and Tchikapa. Consequently, while there are significant divisions to be addressed in Lac Maï-Ndombe, fisherfolk in general are more interested in exploring options for improving livelihoods. In order to overcome these hurdles, the WorldFish Center has introduced an integrated research-extension approach in its interactions with these communities. The teams conducted demonstrations of technological innovations that could significantly improve on present post-harvest fish processing practices, in particular: a solar fish drying tent and a fish smoking barrel.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The influences of clearing native vegetation (Caatinga) in contour strips at 25 cm vertical interval on evaporation losses in cleared strips, annual runoff efficiency and annuall soil loss on gently sloped micro-waterheds in the arid zones of Northeast Brazil are reported. The alternate native vegetation (Caatinga) strips function very effectively as windbreaks thus reducing evaporation losses substantially in the leeward cleared strips. The runoff measured at the micro-watershed with cleared strips was many-fold lower than the runoff obtained at a completely denuded watershed even when it was protected by narrow based channel terraces. However, the annual runoff efficiency can be significantly increased in a strip cleared watershed if narrow based channel terraces are provided on the lower side of cleared strips. The annual soil losses in strip cleared watersheds as well as completely denuded waterhed of gentle slopes were negligible. Thus clearing land in alternate contour strips on a micro-watersheds shall substantially improve crop water use efficiency without creating any significant erosion problems. Additionally this treatment will increase runoff for water harvesting for irrigation purposes.