Catchment Zone Research Articles

Spatial and socio-demographic determinants of South East Queensland students’ school cycling

The low prevalence of Australian students’ utilitarian school cycling could be attributed to the varied and context specific demographic, socio-economic and spatial school travel mode choice determinants. Travel distance is universally important for school cycling and is reliant amongst related home and school spatial proximity factors on a student’s choice of schools. This paper, primarily based on school students’ travel data extracted from the 2009 South East Queensland Household Travel Survey (SEQHTS), examines comparative school cycling travel patterns, school catchment choices and the significant analytical determinants of cycling mode choices from within an urban regional Australian context. Students’ choice of a school external to that located within their designated State school catchment zone was associated with household attributes of parent/guardian employment location, number of income earners and ownership of private vehicles coupled with State school and catchment attributes. Noteworthy variations in school travel distances and modal splits were allied with school catchment choices. Adolescent male students from two parent households owning fewer than two cars and more than two bicycles, with parents/guardians commuting using non-motorised travel modes and resident in Census Collection Districts with conducive cycling environments, contributed largely to the one-way bi-directional primary and secondary school cycling mode shares. This prevalent student cyclist profile indicates the need for enhancements in student school cycling participation, through policies addressing both the spatial (built) and social environment which impact students’ personal and traffic safety coupled with utilitarian cycling image enhancements. Concerted efforts to bolster cycling amongst student segments with current low cycling participation inclusive of females, students from single parent households and those with adequate access to private motorised travel modes may be necessary to further enhance school cycling mode shares. The paper makes a case for individualised targeted travel interventions informed by segregated mode choice determinant analysis for respective primary and secondary school types and directions of school travel.

Does estuarine health relate to catchment land-cover in the East Kleinemonde system, South Africa?

Temporarily open/closed estuaries in South Africa are being subjected to varying degrees of catchment land-cover transformation. Natural landscapes and hydrological functions are integral to the functioning of estuaries. The relationship between catchment land-cover and the health of the East Kleinemonde Estuary was investigated between 2011 and 2013, using geographic information system (GIS) techniques to delineate and quantify land-cover in the whole catchment, in the lower section of the catchment, and in the 1 km and 100 m buffer zones surrounding the estuary. Human activities, as outlined by the Department of Water Affairs resource directed measures (RDM) studies, and their associated land-cover classes are described. Possible links between catchment and buffer zone land-cover class composition and the health of the East Kleinemonde Estuary were explored. There was a relationship between catchment land-cover and estuarine health within all assessed catchment delineations. Natural land-cover was determined to be the best predictor of estuarine health for the East Kleinemonde system. The methods employed in this study can be applied to other temporarily open/closed estuaries in South Africa to prioritise these systems for rehabilitation and/or conservation.

Analytical solution for the catchment zone of a well located near a groundwater divide in a recharged semi-confined aquifer

Summary An analytical solution is presented for delineating the catchment zone of a well located near a groundwater divide in a recharged aquifer. The analytical solution is derived for an infinitely wide, homogeneous, isotropic and uniformly thick semi-confined aquifer. It is shown that the shape and extent of the well catchment zone only depend on the distance to the groundwater divide and on the ratio of the well pumping and groundwater recharge rates. The catchment zone of a pumping well extends beyond the groundwater divide, such that the total area affected at the other side of the groundwater divide equals one half of the well-catchment area, and consists of a part from which groundwater is captured by the well and another part from which groundwater is flowing to the other side but bypassing the well. The amount of groundwater transfer involved equals half of the pumping rate. In case of an injection well, the catchment zone comprises the whole aquifer when the well is sufficiently close to the groundwater divide, and otherwise consist of an infinite but laterally bounded zone in the direction away from the groundwater divide. In both cases, the aquifer at the other side of the groundwater divide gains half of the well injection rate either directly by flow from the injection well or indirectly by capturing groundwater recharge from the other side of the groundwater divide.

Watersheds on weighted graphs

The watershed is an efficient and versatile segmentation tool, as it partitions the images into disjoint catchment basins. We study the watershed on node or edge weighted graphs. We do not aim at constructing a partition of the nodes but consider the catchment zones, i.e., the attraction zones of a drop of water. Often, such zones largely overlap. In a first part, we show how to derive from a node or edge weighted graph a flooding graph with the same trajectories of a drop of water, whether one considers its node weights alone or its edge weights alone. In a second part we show how to reduce the number of possible trajectories of a drop of water in order to generate watershed partitions.

Analytical solution for capture and catchment zones of a well located on a groundwater divide

[1] An analytical solution is presented for capture and catchment zones of a well located on a groundwater divide in a recharged aquifer. The analytical solution is derived for a homogeneous, isotropic, and uniformly thick leaky aquifer. It is shown that streamlines and well-catchment area have elongated shapes tending to infinity along the groundwater divide, and do not depend on any aquifer property, but only on the ratio of the well-pumping rate and aquifer recharge flux. Isochrones delineating capture zones also depend on the mean residence time of the groundwater, which is independent of the well-pumping rate. The capture and catchment zones differ significantly in both size and shape from the classical theory that ignores recharge. In particular, the catchment zone is wider and has a finite extent.

ANALISIS CAKUPAN SITUS-SITUS PERMUKIMAN NEOLITIK DI BANYUWANGI SELATAN

Economic calculations as cost-benefit ratios are used by prehistoric people in exploiting their natural resources. This paper will discuss about landscape and natural resources to reconstruct the site catchment area which explored by Neolithic people at South Banyuwangi in prehistoric times. In the Site Catchment Analysis for traditional farmer, a preliminary of 1-km radius site catchment zone is the most basic or regular subsistence resources, and 5-km radii is largely the maximum limits of radius distance. Based on hypotheses of catchment zone, we analyzed its natural resource inside eachcatchment zone. This analysis conducted on landscape conditions (hills, plains, steep cliffs), water sources (springs, rivers and water basins). Comparison between environmental conditions inside the catchment zone and artifact findings (from survey and excavation work) is obtained to predict the site catchment pattern of Neolithic settlement sites at South Banyuwangi.

1 million community health workers in sub-Saharan Africa by 2015

1 million community health workers in sub-Saharan Africa by 2015

A Phylogeographic Study of the Endemic Rodent Eliurus carletoni (Rodentia: Nesomyinae) in an Ecological Transition Zone of Northern Madagascar

We conducted a mitochondrial phylogeographic study of the endemic dry forest rodent Eliurus carletoni (Rodentia: Nesomyinae) in an ecological transition zone of northern Madagascar (Loky-Manambato) and 2 surrounding regions (Ankarana and Analamerana). The main goal was to assess the evolutionary consequences on this taxon of the complex landscape features and Quaternary ecological vicissitudes. Three haplogroups were identified from the 215 specimens obtained from 15 populations. High levels of genetic diversity and significant genetic differentiation among populations were observed. The different geographical subdivisions of the study area by regions, by river catchment zones, and the physical distance between populations are not correlated with genetic patterns. In contrast, population structure is mostly explained by the geographic distribution of the samples among existing forest blocks. E. carletoni experienced a genetic bottleneck between 18 750 and 7500 years BP, which correlates with periods when moister climates existed on the island. Overall, our data suggest that the complex genetic patterns of E. carletoni can be explained by Quaternary climatic vicissitudes that resulted in habitat fluctuations between dry and humid forests, as well as subsequent human-induced fragmentation of forest habitat.

Delineation of catchment zones of geothermal systems in large‐scale rifted settings

Hydrothermal convection in the Taupo Volcanic Zone (TVZ), New Zealand, is driven by heat extracted at the brittle‐ductile transition, which is in turn supplied by magmatic intrusion of the lower‐crust. We present a numerical model that approximates this circulation in a statistical sense, being constrained by TVZ dimensions and mean thermal properties, but incorporating a permeability distribution of arbitrary heterogeneity. A particle tracking methodology that accounts for advective and dispersive transport is introduced, and ensembles of several tens of thousands of flow paths are constructed for each of the modeled geothermal systems. These flow paths reveal the nature of mass recharge in multicell convective systems, and suggest the ages of waters in TVZ geothermal systems vary between 5 and 50 kyr. Flow path ensembles are used to delineate catchments for each of the modeled systems and a method for calculating their areas is introduced. Catchment area is shown to be proportional to system heat output and area, which is consistent with a 1‐D analytical model of heat and mass transfer. As an approximation to catchments delineated by particle tracking, we outline a method of Voronoi tessellation based on the positions and heat outputs of geothermal systems. This method is used to delineate catchments for geothermal systems in the TVZ and Iceland.

Two in one leachate plume in a karstic aquifer

Some sites formerly used for waste disposal purposes, even if they are closed, continue generating leachate that seeps into the ground and contaminates groundwater in the area where they are located. It is believed that the rainfall being in contact with waste becomes a source of leachate. This fluid seeps into the aquifer and may identify sources of pollution. A modeling work which determined the migration times of solutes in the karstic aquifer of Merida, Yucatan, Mexico, is presented. Both existing and generated information was analyzed; a leachate plume was identified. The methodology used in the study is described, the application of which allowed concluding that this plume was generated from two sources: a waste disposal site and the oxidation lagoons located next to it. The procedure consisted of performing simulations considering the sources that contribute to the development of the pollution plume and forecasting their behavior. With the developed methodology, similar cases can be analyzed to avoid locating catchment zones of drinking water in inappropriate places and/or develop projects to place waste disposal sites that could affect existing catchment areas and to preserve this resource, essential for life.

Bushmeat characteristics vary with catchment conditions in a Congo market

Ever-increasing rates of subsistence and commercial bushmeat hunting in African moist forests result in unsustainable exploitation levels for many mammals. Bushmeat markets are found in a large number of human settlements throughout the region and may be used to monitor the state of game species in catchment areas. As depletion of large-bodied species forces hunters to focus on small-bodied species this is likely to be reflected in the mean body mass and species composition of animals sold in that market. In this paper we present data on bushmeat sold in Basankusu market in the Democratic Republic of Congo during a 2-year period (276 sample days). We counted 10,358 carcasses of 33 mammal taxa, emerging from nine well-defined hunting catchment zone; an area of more than 45,000km2. For each catchment we assessed human pressures using metrics derived from remote sensing. Human population density correlated with higher species richness of species harvested, as well as with an increase in rarer taxa, and with a tendency for more individuals with higher intrinsic rates of reproduction to be observed. We suggest that simple surrogates of anthropogenic pressure and faunal characteristics in markets can be used as a rapid tool to measure faunal depletion of mammals at a regional scale. Such a system of evidence-based game monitoring would allow identification of both potentially overhunted and of less-disturbed areas for consideration in strategic planning.

Effects of Land Use Practices on the Organic Carbon Content, Cation Exchange Capacity and Aggregate Stability of Soils in the Catchment Zones

Problem statement: Land use practice leads to changes in the physico-chemical properties of soils, such as Soil Organic Carbon (SOC), Cation Exchange Capacity (CEC) and Soil Aggregate Stability (SAS) that cause soil erosion. Approach: Merek catchment, Iran suffers from land degradation due to poor land use practice. A study was carried out with the objectives: (i) to determine soil nutrient status in different agro-ecological zones in Merek catchment; and (ii) to evaluate the influence of land use practices on SOC, CEC and SAS. Results: It was found that soil texture was silty and clay, while soil reaction was alkaline (pH was 7.75). The respective amount of carbonates was 32 and 36% in the top-soil and sub-soil respectively, indicating high level of alkalinity in the soils of the study area. The mean SAS of the surface soil layer for agriculture, rangeland and forest was 53, 61 and 64%, respectively with its mean in the topsoil of agriculture is significantly lower (P≤0.05) than the other zones. SOC level in the agriculture, rangeland and forest were 1.35, 1.56, 2.14% in the topsoil and 1.03, 1.33 and 1.45%, in the subsoil of the respective areas. The results of t-test and ANOVA analyses showed that SOC means are significantly different from each other within soil depth and among agro-ecological zones. The CEC in the agriculture, rangeland and forest areas were 25.8, 24.6 and 35.1 cmol ckg -1 for the top-soil and 31.1, 26.8 and 26.9 cmol ckg -1 in the sub-soil, respectively. All the above changes are due to the negative effects of agricultural activities. Conclusion: Improper tillage practice (up-down the slope), conversion of the rangeland and forest to rain-fed areas, crop residue burning, over grazing and forest clearance contribute to reduction in SOC and SAS in the Merek catchment, Iran.

Bacterial community structure and denitrifier (nir-gene) abundance in soil water and groundwater beneath agricultural land in tropical North Queensland, Australia

We explored the microbial ecology of water draining through the soil (lysimeter samples) and in the shallow aquifers (bore samples) underlying sugarcane and banana fields near the Great Barrier Reef (GBR), Australia. Lysimeter and bore water samples were collected and analysed chemically and with DNA fingerprinting methods (PCR-DGGE and clone library sequencing) to characterise the structure of the bacterial community. Bacterial communities in soil water and bore water were distinct (P < 0.05), and a primary factor linked with bacterial community structure was water pH (P < 0.05), particularly in water sampled from lysimeters. Irrespective of treatment, >80% of all rRNA gene sequences originated from proteobacteria. However, groundwater communities differed from those in soil water by greater occurrence of Neisseriales and Comamonadaceae (P < 0.01). qPCR was used to measure copy numbers of the nirK and nirS genes encoding NO-forming nitrite reductases. Copy numbers of both genes were greater in soil water samples than groundwater (P = 0.05), with the difference in nirK being greater under sugarcane than banana. These differences in nirK-gene abundance show that there is greater potential for denitrification in soil water under sugarcane, leading to low concentrations of nitrate in the underlying groundwater. This knowledge can be used towards development of soil and land-use management practices promoting bacterial denitrification in groundwater to lessen the undesirable ecological consequences where groundwater discharges lower in the GBR catchment zones.

An assessment of biomass feedstock availability for the supply of bioenergy to University College Dublin

As the cost of energy rises due to an increase in fossil fuels prices, the need to develop a sustainable alternative that will reduce green house gas emissions has increased in importance. One such alternative to reduce dependency on fossil fuels is the use of biomass for bioenergy generation. This study aims to quantify how much biomass can be produced in a specific area with a maximum haulage distance of 75 km to its end location, in this case, a large residential campus, to supply fuel to a biomass boiler. The study is carried out by identifying potential sources of biomass within the catchment zone and then quantifying it under different scenarios. The first scenario focuses on minimum land use impact, which quantifies how much biomass could be achieved taking just 10% of biomass from the sources identified. The second scenario is the maximum energy scenario and is set out to establish the maximum amount of energy that could be generated within the catchment zone using 50–100% of available biomass. The final scenario is the environmental scenario which looks to quantify biomass while not infringing on existing land uses such as agriculture and forestry. Results show that scenario one could produce almost 6 PJ of energy which is, scenario two could produce over 31 PJ of energy and scenario three could produce almost 14 PJ of energy.

Geological and structural influence on groundwater distribution and flow in Ngong area, Kenya

Groundwater is increasingly becoming an important resource within and around the Ngong area, of Kenya. This is mainly as a result of increase in human population due to rural-urban migration, industrial expansion and farming activities. Ngong area forms a water catchment zone to the west of the city of Nairobi in Kenya. The geology of the area is comprised of volcanic layers of basalts, trachytes, phonolites and tuffs all overlain by thick layers of clay soil. The soil retains water for an extended period of time after the rains and this partly recharges aquifers in the area. Basalts and trachytes form good aquifers whereas tuffs are aquifers only when fractured. Faults delineated from a study of aerial photographs trend in a North-South direction in conformity with the structural pattern of the eastern branch of the Great Rift Valley. The influence of the faults on groundwater is two fold. They act as drainage channels to the flow of groundwater and also as aquifers in the area.

Multi-year monitoring of estuarine sediments as ultimate sink for DDT, HCH, and other organochlorinated pesticides in Argentina

Forty-nine superficial sediment samples used in this study were collected from eight sites in the Bahia Blanca Estuary, located in the Buenos Aires Province southwest, Argentina, in a period between April 2005 and March 2009, to assess the concentration levels, spatial and seasonal distribution, and putative input sources of 18 selected organochlorine pesticides (OCs), following UNEP-IAEA procedures. Average concentration levels in sediments ranged between 3.54 and 63.79 ng g⁻¹, d.w. (mean = 15.99 ng g⁻¹, d.w.), for ∑OCs, and from nondetectable to 8.03 ng g⁻¹, d.w. (mean = 2.16 ng g⁻¹, d.w.), and from nondetectable to 3.20 ng g⁻¹ (mean = 0.97 ng g⁻¹, d.w.) for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs), respectively. Principal component analysis allowed the classification of sampling sites according to the main OCs inputs over the estuary. In comparison to other worldwide locations and to the world coastal sediment concentrations range, sediment DDTs and HCHs levels were in the low range; on the opposite, ∑OCs average was in the medium range. OCs seasonal distribution was found to be highly correlated with the precipitations seasonality and sowing seasons in the adjacent agriculture fields. In addition, an ecotoxicological risk assessment pointed industrial and agriculture catchment zones with intermediate probability of adverse effects to biota, while the city sewage outfall was classified with none indication of an immediate threat. Data indicated that the estuary sediments were functioning as a sink for persistent OC pesticides (either in use or banned), however, it was found a declining trend on their environmental burden.

Major, trace and REE geochemistry of the Ganga River sediments: Influence of provenance and sedimentary processes

The sediments of the Ganga River from different depositional regimes in the Plain region such as the river channel, active flood-plain and the older flood-plain sediments from the inter-fluve region were analysed for major, trace and the rare earth elements (REEs). These are compared with catchment zone sediments of the river and probable source rocks in the Himalaya. The lower CIA values between 48 and 54.7 for the catchment sediments indicates that the sediments supplied to the Ganga Plain are chemically immature and subjected mostly to physical weathering due to higher erosion rates in the Himalaya. The CIA values ranging between 55 and 74, with average value of 59, 61.4 and 67 for sediments from the Plain's bed-load, active flood-plain and older flood-plain from the inter-fluve region indicates that silicate weathering of Ganga River sediments has occurred only after entering into the plains. This is likely because of higher residence time and change in the climate from cold-frigid in the Himalaya to tropical sub-humid in the plains. Therefore, the use of geochemical data on ancient system to infer climate in their source region may not always be true. Although the CIA values indicate a moderate chemical weathering in the plains, it is far from impressive. Dominance of physical weathering in the catchment region and lower degree of chemical weathering in the Plains indicate that weathering of sediments supplied by Himalayan Rivers, particularly the Ganga River may not have affected the atmospheric CO 2 to a significant level as is generally believed. Thus the net effect of the Himalaya on the CO 2 sequestration and consequent global cooling needs a re-evaluation. The plots of sediments in ternary diagram among La, Th, Sc and ratios involving Co/Th, La/Sc and Sc/Th indicate granitic to granodioritic source rocks to the sediments. The ratio plots involving relatively immobile Al 2O 3, TiO 2 and FeO along with REE plots suggest that out of the major Himalayan lithologies, gneisses and Cambro-Ordovician granites of HHCS have acted as the dominant source to the sediments. The plots of LogNa 2O/K 2O vs. LogSiO 2/Al 2O 3 and FeO/SiO 2 vs. Al 2O 3/SiO 2 diagrams show that the combination of processes including erosion, weathering, sorting and aeolian activity has together played a major role in progressively changing the chemistry from source rock to catchments bed-load to Plains bed-load, active flood-plains and the older inter-fluve sediments in the Ganga River system. The above plots demonstrate that as a result of above processes the ratios between the elements generally thought to be immobile and used in provenance studies does not always remain invariant and the linear trend line in the scatter gram between the two immobile elements show rotation around the fine grained end member.

Migration and venting of deep gases into the ocean through hydrate-choked chimneys offshore Korea

It has recently been recognized that, in addition to low concentrations of widespread natural gas hydrate associated with bottomsimulating seismic refl ectors, highly concentrated hydrate can occur in local seafl oor fl uid venting structures. Such structures extend upward into the regional gas hydrate stability fi eld and sometimes allow gases to escape into the overlying ocean. These hydrate-choked chimneys are especially prospective as an energy resource because they contain high hydrate concentrations. Furthermore, they may be one of the most important conduits into the ocean-atmosphere system for deep methane. We present an analysis of two-dimensional seismic refl ection data from offshore Korea that give a complete picture of gas migrating from a deep source zone to feed hydrate-choked vent structures at the seafl oor. The gases migrate upward through networks of fractures imaged as steep amplitude striations in both diffuse and concentrated distributions. We present an example of a high-fl ux gas vent fed through fracture swarms emanating from a 10‐15-km-wide catchment zone of source gases residing 3‐4 km below the seabed. The geological context and the inferred distribution of hydrate within this feature are consistent with recent models in which seabed gas venting is a consequence of elevated pore fl uid salinities that are produced by a high fl ux of gases migrating independently of the pore water. In contrast, a nearby vent that is not plumbed into the same high-fl ux system appears to be dominated more by gas-rich liquids. We present these two vent structures as type cases for high- and lowfl ux fl uid escape systems in the seabed. Furthermore, we suggest that since the amount of gas trapped as hydrate within the vents is small compared with the amount in the underlying reservoir, the greatest risk for increased methane input to the atmosphere associated with climate-driven oceanic warming is not the melting of hydrate, but an increase in the number of deep reservoirs able to vent gases through the seabed that occurs as the regional gas hydrate stability zone thins.

Assessment of Holocene surface hydrological connections for the Ounianga lake catchment zone (Chad)

A hydrological perspective to the recent sedimentary analysis conducted at Lake Yoa (Ounianga region, NE Chad) is proposed. The complex hydrological and hydrogeological situation alters the climatic stress. The potential paleo-water network and lake levels have been computed based on SRTM elevation information and ArcGis software. Results show that Lake Yoa is situated in a favorable location, and in addition to continuous input from the Nubian Sandstone Aquifer System (NSAS), it could benefit from river input from distant recharge areas, including the Tibesti Mountains and a large catchment area in the Erdis. Water budgets for 6000 cal yr BP reconstructed conditions show that the maximum lake level (40 m above its present level) was probably maintained relatively easily by surface and subsurface water.

Competition within the Airport System of the Republic of Croatia

The Republic of Croatia is extremely well covered by airports, especially in the coastal area. The catchment zones overlap both within the Croatian airport system and the adjacent airports in the neighbouring countries. Market liberalization has resulted in competition among several air carriers as well as in the competition among airports. The work analyses the conditions in air traffic, concentration on the air traffic market in Croatia and it analyses the competition by using multi-criteria method SMART.