Intensive biomass production in emerging bioenergy systems could increase nonpoint-source sediment and nutrient losses and impair surface and groundwater quality. Recycling biochar, a charcoal byproduct from pyrolysis of biomass, provides potential sources of mineral nutrients and organic carbon for sustaining biomass productivity and preserving soil and water. Yet, research is needed to verify that recycling of pyrolysis biochars will enhance crop growth and soil and environmental quality similar to black carbon or biochar derived from burning of biomass in tropical or Terra Preta soils. The experimental design of this study consisted of 3 replications and four biochar rates (0, 4, 16, and 64 Mg ha-1) incorporated in both a sandy loam and clay soil with and without fertilizer sources of N, P, and K. The sandy loam and clay soils were studied in separate experiments within a set of 24 box lysimeters seeded with switchgrass. Simulated rain was applied at 50 percent and 100 percent establishment of switchgrass for each soil type. Runoff and leachate were collected and analyzed for total and dissolved N, P, K and organic C. After the second rain event, each soil type and the accumulated switchgrass was sampled and analyzed. In the Boonville soil, biochar applied at 64 Mg ha-1 decreased switchgrass emergence from 42 percent to 14 percent when compared to soil alone. In the Burleson soil, 64 Mg ha-1 biochar had no effect (P > 0.05) on biomass production or leaf area index (LAI). Fertilizer N, P, and K had no effect (P > 0.05) on switchgrass emergence for either soil, but did increase (P < 0.001) N, P, and K uptake, biomass production, and LAI. Increasing rates of biochar increased (P < 0.001) runoff concentrations of DRP during each rain event for both the Boonville and Burleson soils. Four rates of biochar receiving supplemental N, P, and K fertilizer also resulted in greater runoff concentrations of DRP. Emergence tests under increased heat showed electrical conductivities of soil-water solutions to be as high as 600 microS cm-1, even after biochar was washed with acetone and water to remove residual oils and tars and soluble salts. Increasing biochar rates decreased soil bulk density and increased pH and SOC in the 0- to 5-cm depth of soil. As a result of high nutrient recovery during pyrolysis (58 percent of total N, 86 percent of total P and 101 percent of total K), high rates of biochar applied at 64 Mg ha-1 increased mass losses of TN, TP, and TK from both soils. Yet, the mass balance of nutrients showed a surplus of N, P, and K at 64 Mg ha-1 biochar, which suggests some nutrient inputs are not plant available and remain in soil. Careful management of biochar, especially at high rates with these high nutrient contents, is critical when trying to improve soil fertility while protecting water quality.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 193-202).

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains ix, 149 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 60-63).

This paper presents the results of an experimental study aimed at determining the impact of porous asphalt on the quality of stormwater runoff on highways with a curb and gutter drainage system. A porous overlay, also known as permeable friction course (PFC), is a layer of porous asphalt applied to the top of conventional asphalt highways at a thickness of 50 mm to improve safety and water quality and reduce noise. The quality of highway stormwater runoff was monitored before and after the installation of PFC on an eight-lane divided highway in the Austin, Texas area for 15 months. Observed concentrations of total suspended solids from PFC are more than an 80% lower than from the conventional pavement. Concentration reductions are also observed for nitrate/nitrite and total amounts of phosphorus, copper, lead, and zinc. The data shows that the results with curb and gutter are consistent with past results where runoff sheet flowed onto vegetated shoulders. / text

Rising global air temperatures are causing increased melting across the surfaces of large ice masses such as the Greenland Ice Sheet and the ice caps of Arctic Canada. The fraction of this melt that refreezes within the snow and firn has a large spatial variability across the surfaces of these ice masses. This spatial variability is an important control on the surface mass balance, and has important implications for the interpretation of satellite radar altimetry data sets. The sensitivity of large ice masses to climate change depends on changes in the melt-runoff relationship, and changes in the spatial extents of surface snow zones within the accumulation zone. Therefore, this thesis develops a model used to calculate melt, near-surface refreezing and surface runoff across the surface of a large ice mass. The model is used to predict both stratigraphic changes and bulk snow and firn properties over a melt season across a transect of points. A high-resolution snow and firn data set from Devon Ice Cap is used to calibrate and validate the model. It is then run across a transect covering the entire altitude range of the ice cap for the summers of 2004 and 2006. The model matches measured trends in bulk snowpack variables across the transect in both years. Calculated fraction of melt running off is similar in both years at ~44%, though is sensitive to change in air temperature. Surface mass balance (including internal accumulation), found to be +0.26 Gt in 2004 and +0.18 Gt in 2006, changes in a parabolic way for a linear air temperature change. The model is then applied to the Greenland Ice Sheet without altering any of the calibrated parameters. It is run for two melt seasons, 2004 and 2005, over which model output compares well with measurements of snow depth, sub-surface density and altitudes of snow surface boundaries. The wet snow line responds in a linear way to change in air temperature, and the runoff line is sensitive to the specified depth within the firn of the impermeable layer. Over the next century, the model shows that the dry snow zone will disappear completely under moderate warming scenarios, and the percolation zone will also disappear under intense warming scenarios. Including a more complicated representation of vertical meltwater percolation through the snow and firn grid substantially alters modelled autumn density profiles, and produces more accurate values of meltwater percolation depth and ice fraction within the autumn snowpack. However, bulk snowpack properties are of similar accuracy to the un-modified model. Scaling up of the model, in both spatial and temporal terms, will make it useful for assistance in the interpretation of satellite radar altimetry data sets, as well as assessing future changes in the spatial variability of refreezing and runoff, reducing the uncertainty in long term surface mass balance predictions across large ice masses.

The Mfolozi, the second largest catchment in KwaZulu Natal, is already severely degraded over substantial areas. Its mean annual sediment load is extremely high and deposits on its floodplain have caused very serious financial losses. Previous studies in the catchment have attributed its soil loss to poor land use practices by peasant farmers. There is a concern that this production will be substantially increased by land use changes incumbent on the land reform programme. In order to ensure that this programme does not lead to increased degradation and exacerbate associated environmental and socio-economic problems, this study identified both subcatchments and land types that are highly susceptible to erosion and already highly eroded. An unpublished map showing the location of 19 categories of erosional forms and three categories of extreme relief features was available for use. The density (and areal extent in the case of badlands) of each of these forms within each of the 16 possible land types within each of the 43 subcatchments, was obtained and related to their dominant physiographic variables. The findings revealed that the catchment is not as severely or extensively eroded as suggested by previous studies. A substantial portion of the former Natal areas, mostly targeted for reallocation, have however, been shown to be unsuitable for this purpose. / Thesis (M.A.)-University of Durban-Westville, 1996.

The Rowden Moor experimental site (A.F.R.C. I.G.E.R., North Wyke) provided an opportunity to characterise discharge regimes, elucidate runoff generation mechanisms and to consider implications for solute movement under natural and drained conditions. Research was conducted on a heavy clay grassland soil in an area of high rainfall (1053 mm a ˉ¹) in South West England. A combined hydrometric and tensiometric study was undertaken within a nested experimental design (1 m² to 1 ha) on one undrained and one drained site throughout a drainage season (October to March). Results at the hectare scale demonstrated that drainage did not substantially alter the volume of field runoff ( ~ 400 mm) but did change the dominant flowpaths. Drainage diverted water from surface/near surface routes to depth so that drain storm runoff was lagged by some 30 minutes over undrained site discharge. The drained site also exhibited a more peaky regime, with a maximum daily discharge of 45 mm being almost twice that for the undrained field. At the field and plot scale, the significance of macropore flow was noted. To investigate this in more detail, a tracer experiment was performed on an isolated soil block which had been mole drained and so had enhanced macroporosity. Macropore flow was generated under unsaturated conditions (little matric potential response and no water table was identified). Stable oxygen concentrations were δ18O +3.5 and -5.8 in tracer and background water respectively. Drainflow indicated that there was rapid interaction between applied tracer and soil water (peak flow δ18O -1.1). Thus, the matrix-macropore interface was not a boundary between two separate domains of old and new water, high and low conductivity but a site of rapid interchange and mixing. Temporal variability of soil status and malric water composition, also indicated that limited areas of the matrix were capable of transmitting rapid flow. It became clear that even in a heavy clay soil such as that found at Rowden, where macropore flow was promoted by drainage operations, the matrix still had an important role to play. On the basis of potential, soil moisture and observation of tracers, it is proposed that discrete (finger-like) volumes of the matrix are capable of rapid water transmission. Although it was frequently impossible to relate moisture content and soil water potential because instrumentation monitored different volumes of soil, hysteretic soil moisture behaviour over the drainage season was evident in both data sets. This study confirmed the importance of rapid subsurface runoff generation mechanisms on drained soils, but noted that discontinuous translatory flow in the matrix and macropore flow occurred and that the two ‘domains’ were inextricably linked. Further work should be undertaken at the detailed scale to elucidate the soil characteristics which promote rapid runoff mechanisms and the consequences for water quality, especially where the soil subsurface represents a major reservoir (e.g. nitrates).

An examination of research and information needs in urban hydrology suggested the investigation of urban water balances and micro- hydrological processes. This should facilitate more accurate modelling of the rainfall-runoff process from urban impermeable surfaces. Greater London data produced annual water balances for 5 heavily urbanized Thames tributaries and estimates of the annual yield ranging from 12-72%. Mean annual runoff for largely rural basins in South East England in comparison was 15-44% of rainfall. The inadequacy of the data for water balance studies led to the instrumentation of a small urbanized catchment at Redbourn, Hertfordshire. Standard meteorological measures were recorded. New instrumentation was designed to measure runoff from shallow pitched roofs while commercially produced instruments were adapted and installed to monitor runoff from a block of flat asphalt-and-chippings garage roofs, and runoff from asphalt roads and pavements at the highway drain outfall. Runoff from these impermeable surfaces is less than 100% even during winter months when evaporation is low. Percentage runoff is 76% for both the pitched and flat roofs while that from the paved surfaces is only 17%. Despite differences in slope, runoff volumes from the pitched and flat roofs are almost identical suggesting that the flat roof does not afford much greater depression storage and evaporation losses. The flat roof does however attenuate storm runoff producing lower flow rates and longer runoff duration than the pitched roofs. Road runoff is very low because of infiltration. The calculated depression storage is 0.25 mm for both roof types and 1.00 mm for the road surface. An average water balance compiled for the roofs gave evaporation as the residual 19% of rainfall. Using an average roof evaporation rate in the road surface water balance gave infiltration as 36% of rainfall with 17% runoff, 21% evaporation and 26% depression storage. Runoff from metre-square roof samples produced slightly different percentage runoff figures for the same winter period. Average percent runoff from red Redland 49 tiles (set at 30°) was 98%, grey Stonewold tiles (set at 17½°) produced 85% and asphalt roofing felt produced 38% runoff. These results are evaluated in the light of probable errors in measurements.

Two catchments were investigated to determine whether the "first flush" effect was likely to occur in metropolitican Adelaide, South Australia. The residential catchments chosen were located in at Halsey Road, Henly Beach South and Riverway, Fulham Gardens; their areas were 155 ha and 18 ha respectively. / Thesis (MEng(CivilEngineering))--University of South Australia, 2001.

Two catchments were investigated to determine whether the "first flush" effect was likely to occur in metropolitican Adelaide, South Australia. The residential catchments chosen were located in at Halsey Road, Henly Beach South and Riverway, Fulham Gardens; their areas were 155 ha and 18 ha respectively. / Thesis (MEng(CivilEngineering))--University of South Australia, 2001.