Phosphorus Export From Two Contrasting Rural Watersheds in the (Sub) Humid Ethiopian Highlands

Establishing worldwide sustainable and phosphorus efficient cropping systems is urgently needed because the supply of suitable phosphate rock is limited, and excess phosphorus in streams causes eutrophication. One of the impediments in the developing world for sustainable P practices is the lack of studies on P transport and its eventual disposition in the environment. One of these regions with few studies is the Ethiopian Highlands, with permeable volcanic soils. The objective was to establish baseline data on P watershed export in the (sub)humid highlands. Two contrasting watersheds were selected near Lake Tana. For 2 years, stream discharge and sediment, total P, dissolved P, and bioavailable particulate P concentrations were determined at the watershed outlet. The first watershed is the 57 km2 Dangishta, with lava intrusion dikes, forcing subsurface flow through faults to the surface and preventing gully formation. Subsurface flow was half of the 1745 mm annual precipitation, and surface runoff and erosion were minimal. The second watershed is the 9 km2 Robit Bata with 1,420 mm precipitation. The banks of several river banks were slumping. The upper part of the watershed generates saturation excess runoff. A hillslope aquifer in the lower part provided interflow. The average sediment concentrations of 10.5 g L−1 in the stream in Robit Bata (11 times that in Dangishta) reflected the sediments from banks slipping in the stream. The hydrology and the soil loss directly affected the phosphorus export. In Dangishta, the total P concentration averaged 0.5 mg L−1 at the outlet. In Robit Bata, the average total P concentration was 2 mg L−1. The bioavailable particulate P concentration was only twice the concentration in the runoff water. The low phosphorus content of the subsoil slipping in Robit Bata moderated biologically available particulate P at the outlet. Average dissolved P concentrations for both watersheds were around 0.1 mg L−1 in the low range found in temperate climates. It reflects the difference in length of time that phosphorus fertilizers have been applied. Our research concludes that commonly implemented practices such as strengthening river banks and stabilizing gully might not lead to improved water quality in Lake Tana.

GIS Based Analysis of Niger-Benue River Flood Risk and Vulnerability of Communities in Kogi State, Nigeria

Flood remains one of the most common natural disasters. Its rate of occurrence and the associated destructive tendency are on a rising scale across the globe. Flood risk may increase due to human activities. It could also decrease by appropriate flood management and planning. However, this requires upgraded and newly generated reliable and up to date floodplain and flood vulnerability maps. Hence, this study analysed the Niger-Benue river flood risk and vulnerability of 256 communities in Kogi State. The aim is to generate reliable up to date flood vulnerability maps that categorises the communities into different vulnerability zones and identify likely locations for erecting flood shelter/refugee camps during flood events in the State. Shuttle Radar Topography Mission (STRM) Digital Elevation Datasets, the spatial location of 256 communities, shapefiles of Kogi State’s administrative boundaries and Niger-Benue river basin were among the datasets acquired for the study. The Digital Elevation Model (DEM) of the study area was created to depict topography and the heights of each component of the terrain. Also, a 3km buffer distance was created around the Niger-Benue river and four vulnerability zones were defined based on the terrain and proximity components of each community. Furthermore, choropleth maps were generated for each vulnerability zone based on the number of communities per Local Government Area (LGA). Findings of this study revealed that out of the 256 sampled communities, 161 representing 62.89% are exposed to varying degrees of vulnerability due to Niger-Benue flooding. Out of these, 33 (12.89%) are highly vulnerable, whereas each of the vulnerable (64) and marginally vulnerable (64) communities accounted for 25%. The rest 37.11% constituted the not vulnerable communities (95). Out of the highly vulnerable communities, 27.27% accounted for those located on river banks and 72.73% for those located within a 3km distance from the river. The majority of the riverbank communities were found in Kogi, Lokoja and Ajaokuta LGAs. Igalamela Odolu, Kogi, Ofu and Bassa were among the LGAs with a high number of vulnerable communities. The not vulnerable communities were mostly located around the Agbaja Plateau and Okoro-Agbo hills in Ijumu, Kabba/Bunu and Yaba East LGAs. It was concluded that the 9 communities (Ajaokuta, Eroko, Iche, Jamata, Numai, Okume, Agodo, Denbor and Gunji Twaki) located on river banks are exposed to the highest level of flood risk and invariably, the devastating impact of flood in Kogi State. Most communities in Ijumu, Kabba/Bunu and Yaba West LGAs are less likely to be affected by Niger-Benue River flooding. It is therefore recommended that communities within the highly vulnerable zones, beginning with the 9 located on river banks should be relocated to higher terrains. Also, future settlement development should be discouraged in the zone by the collaborative efforts of the State and LGA authorities. Further studies should be conducted around Ijumu LGA in view of identifying the most suitable locations for possible flood shelter/refugee camp development in the study area.

The Chicago Riverwalk: urban sustainability lessons

PurposeThis paper reviews, summarizes and pieces together scattered information on the newly completed Chicago Riverwalk in Chicago, Illinois. It explains the design process that transformed an outmoded infrastructure and disused river banks into an attractive gathering civic space, a linear urban park and a functional transportation corridor.Design/methodology/approachLiterature review.FindingsOverall, the paper reports on one of the latest projects in Chicago that symbolizes the city's long history and earnest commitment to urban sustainability.Research limitations/implicationsThe paper identifies key urban sustainability lessons that are transferable to other cities.Originality/valueIt is the first paper that stitches together scattered information on the topic.

Three-dimensional niche partitioning between two colonially nesting ardeid species in central China

Background Interspecific competition is known to be strongest between those species that are both closely related and sympatric. Egrets are colonially nesting wetland birds that often overlap and can therefore be expected to compete in roosting and nesting habitat as well as in diet. According to the niche partitioning hypothesis, it is to be expected that these similar species would show differentiation in at least one of the main niche dimensions to reduce competition. We tested niche partitioning between the colonially nesting Little Egret (Egretta garzetta) and Cattle Egret (Bubulcus ibis) in temporal, spatial and trophic dimensions. Methods Field study was conducted in three mixed egret colonies in Yangxian County, southwest Shaanxi Province, central China. For each nest colony we recorded its spatial location, the height of nesting trees and of nests, the height of roosting trees and of roosting individuals within the trees. We determined the first egg-laying and first hatching dates of the two species. Craw dissection of storm-killed egret nestlings was used to measure the diet. Six transects were surveyed to study foraging habitat selection. Results We found that hatching time of Little Egrets peaked earlier (by about 1 month) than that of Cattle Egrets. Cattle Egrets nested and roosted higher than Little Egrets. The foraging habitats used by Little Egrets were dominated by river banks (73.49%), followed by paddy fields (13.25%) and reservoirs (10.84%), whereas Cattle Egret foraging sites were characterized by grasslands (44.44%), paddy fields (33.33%) and river banks (22.22%). Little Egrets consumed more fishes (65.66%) and Odonata larvae (13.69%) than Cattle Egrets, while Cattle Egrets were found feeding mainly on Coleoptera (29.69%) and Orthoptera (23.29%). Little Egrets preyed on larger mean biomasses of food items than Cattle Egrets. Conclusions Our results confirm the niche partitioning hypothesis as a mechanism for coexistence among ecologically similar species. In two coexisting egret species, niche partitioning is multidimensional, such that the two coexistent species occupy differing ecological space based on all three temporal, spatial and trophic niche dimensions.

VASCULAR PLANTS COLONIZATION OF THE HISTORICAL CITY OF AZEMMOUR, MOROCCO

From its Portuguese period, the historical city of Azemmour, on the Oum Errabia River banks, still boasts several monuments, including an imposing fortified wall. Among the factors of degradation that threaten this wall, we are particularly interested in the plant’s action growing over this monument. The objective was to start by establishing a list of plant species colonizing the wall, then to deduce the potential effects that vegetation can have on the substrate. We carried out a systematic sampling in Azemmour. After sampling and identifying the plants, we established a list of 58 species, belonging to 26 families and 49genera. TheAsteraceae family is the most represented with 11 species, followed by Solanaceae with 6 species, Poaceae with 5 species and Amaranthaceae with 4 species. Depending on their life form category, these plant’s roots are more or less intense, which leads to the dismantling of the masonry, and ultimately threatens ruin. The many medicinal plants found in the area are also a source of pressure on the site as they are anarchically uprooted by users. Devegetation measures must be undertaken urgently by conservators to control the spread of these plants in order to preserve the historic heritage.

Cyperus difformis (small-flowered nutsedge).

C. difformis is a sedge which is listed in Holm's list of the world's worst weeds, being a problem especially in rice, sugarcane, tea and maize. It is a dominant weed in direct-seeded rice when it occurs in high plant densities; forms dense mats of vegetation in the young crop and can cause rice yield losses of 12-50%. It is native to the tropics of the Old World, but is spreading well outside its native range. It has a relatively short generation period of as little as 4 to 6 weeks from seed to seed. It can spread along waterways and grow in disturbed sites, lake margins and on river banks.