Effect of Declining Rainfall and Anthropogenic Pressures on Three Wetlands Types in Lesotho (original) (raw)
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Journal of Rural and Development, 2017
Wetland hydrology is important in understanding wetland systems, evaluating wetland functions and processes and assessing wetland conditions. Wetlands assimilate and transform pollutants and nutrients ensuring that quality water is discharged from the wetland into streams. The objective of this study was to characterise wetland hydrology and evaluate the water quality so as to determine the ecological functioning of the Khalong-la-Lithunya wetland. Wetland hydrology and water quality of the three sub-catchments were monitored from October 2015 to March 2016. Water levels in piezometers were recorded once a month and monthly water levels data for the years 2010, 2011, 2012 and 2013 previously recorded by the Millennium Challenge Account-Lesotho (MCA-L) project were integrated to this study’s data. Rainfall, piezometer and stream water were similarly obtained once every month. These were analysed for δ2H and δ18O water stable isotopes and water quality parameters determined. The estim...
There is sparse information on the characteristics of the wetlands in the Khalong-la-Lithunya catchment (KLC), Lesotho in terms of physico-chemical properties, soil organic pools and vegetation isotopic signatures and hydrochemistry of surface waters after five years of rehabilitation. At the KLC two transects of length 250 m-700 m were chosen and soil observations made at intervals of 50 m and at these points, piezometers were installed in duplicates and water samples were collected from Jan to Dec for four years (2009)(2010)(2011)(2012). Soil samples were collected in duplicate from excavated mini-pits (0.50 m). Vegetation samples were collected monthly (Jan, Apr and Aug) of 2010 from these transects (upper slope, middle and toe-slopes) on which δ 15 N isotope was applied. Samples (soil, water and plant) collected were properly labelled and transported to the laboratory. Samples were analysed after standard method. Results showed that soil organic carbon varied significantly across mini-pits, and transects. These ranged from 15.50 g kg −1 with a mean of 28.61 g kg −1 (Transect-1) to between 34.60 and 53.50 g kg −1 with a mean of 43.24 g kg −1 (Transect-2). Majority (or 78%) of the pedons in Transect-1 are strongly weathered, while in Transect-2, majority of the pedons (i.e. 73%) were classified as non-or weakly weathered using soil organic matter: silt + clay ratio. Results of the cluster analysis showed that clusters 1, 2, 3 and 4 were related to the water holding capacity, the soil weatherability, the soil ability to store carbon (carbon mitigation) and the soil's acidity. Results of the δ 13 C data for both transects varied slightly with slope positions though not significantly different (p b 0.05) but higher negative values of the vegetation −28.13 to −28.90‰ were observed. The results of the δ 15 N ranged from −2.52‰ to −2.93‰ with a mean of − 2.81‰. Results of the hydrochemistry from the installed piezometers showed that across years and months the following variables (pH, EC, Ca, Mg, Na, K & NO 3 -N) were within the normal range stipulated by the WHO , while the phosphate concentrations were beyond the limits of the USEPA/NOAA (1988). It was concluded that more research is needed to identify sources and forms of phosphates in this wetland.
Soil Science - Emerging Technologies, Global Perspectives and Applications [Working Title], 2022
Monitoring is essential to evaluate the effects of wetland restoration projects. Assessments were carried-out after 6 years of restoration efforts on a wetland located in two agro-ecological zones (AEZ): the Mountains agro-ecological zone–Khalongla-lithunya (KHL) and the Foot Hills–Ha-Matela (HM). The former was under conservation and the latter non-conserved. Mini-pits were dug along transects for soil sampling. Runoff water was collected from installed piezometers into pre-rinsed plastic bottles with de-ionized water once a month for between 3 and 6 months. Soil and water samples were analyzed in the laboratory for Ca, Mg, K, Na, total nitrogen, and phosphorus, and soil samples were further analyzed for Cu, Fe, Zn, and Mn and vegetation isotopic N15. Water quality, soil organic matter (SOM), carbon pools, base cations, ratios (silt:clay & SOM:silt clay), texture, and N-15 isotopes were chosen as indicators. Results showed that base cations were significantly (p
Wetland water balance assessment: a case study of the Sosa wetland, Maseru, Lesotho
Water Practice and Technology
The Sosa wetland is a sensitive wetland, situated at the headwaters of the Jordan catchment in Maseru. Due to unregulated land use activities in the past decades (2010–2020), the Sosa wetland nearly dried up resulting in a water shortage. Therefore, this study performed a wetland water balance of the Sosa wetland in Lesotho for the period of 1975–2020 using GIS and remote sensing. Landsat imageries of 1975–2020 were used for land use and land cover while the Penman–Monteith and Thornthwaite methods were used to estimate evapotranspiration. Results show that water/marsh, cultivation, settlements and bare-land increased by 2.04, 4.1, 5.82 and 28.71%, respectively, from 1975 to 2020. Forest and shrubs as well as grasslands decreased by 38.83 and 1.76%, respectively, from 1975 to 2020. Evapotranspiration estimates for the period 1984–2020 were in the range of 900–1,071 mm/year which is substantially greater than the annual mean rainfall of the catchment which ranges from 550 to 850 mm/y...
KOEDOE - African Protected Area Conservation and Science
Conservation implications: The study can be invaluable to wetland scientists, managers, biodiversity conservationists, water resource managers and planners and vegetation ecologists in Southern Africa. About 70% of Lesotho falls in the Maloti-Drakensberg, accounting for about 60% of the region, and this makes the study important in biodiversity conservation planning, particularly in the Highlands. The wetlands in Lesotho face severe anthropogenic pressures that include overgrazing and economic development. Given that the Lesotho Highlands as a water catchment is not only important for Lesotho, but also for South Africa and Namibia, the conservation of the associated wetlands and this critical water resource is indispensable.
Ecosystem services of high-altitude Afromontane palustrine wetlands in Lesotho
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Although wetlands are among the most valuable ecosystems, the condition and extent of wetlands is declining worldwide, to the detriment of ecosystem service delivery. This study assessed the ecosystem services delivered by the Afromontane palustrine wetlands of Lesotho using the WET-EcoServices tool and explored the relationships of the services with environmental factors and plant functional traits using ordination techniques. Higheraltitude wetlands differed from the lower-altitude wetlands in the spectrum of services they deliver. These wetlands were mostly valued for carbon storage, provision of natural resources, streamflow regulation, maintenance of biodiversity and erosion control. Lower-altitude wetlands were valued for natural resources, cultivated foods, nitrate removal, phosphate trapping and streamflow regulation. The environmental factors affecting the delivery of ecosystem services most were altitude, longitude (directly correlated with rainfall in the context of Lesotho), landscape, soil parent material, slope and soil depth. The delivery of several services was also correlated with plant functional traits, for example, carbon storage and maintenance of biodiversity were positively correlated with plant shoot mass, total plant biomass and rooting depth. The location and environmental characteristics of a given wetland within a catchment and the functional characteristics of the wetland's dominant plant species have an influence on the ecosystem services that it delivers. However, the level of threat to ecosystem services is high, especially in the lower-altitude wetlands. The threats, which are mainly anthropogenic, are mostly associated with crop cultivation, overgrazing and trampling by livestock and economic development. Thus, for sustainable provision of wetland ecosystem services, these Afromontane palustrine wetlands require urgent attention and up-scaling of the conservation efforts. 1. Provisioning ES, which are the tangible products ("goods") that are delivered by the wetlands, e.g. food, fibre, freshwater, timber, natural medicines, land for cultivation and grazing for livestock;
Physicochemical and Biological Characteristics of Two Ethiopian Wetlands
Wetlands, 2013
Wetlands serve as important natural resources and play a major eco-hydrological role in environmental management. However, information about the potential anthropogenic threats to Ethiopian wetlands is lacking; therefore an investigation was conducted to assess the physicochemical and biological characteristics of two Ethiopian wetlands. The results clearly suggest that there is a high level of anthropogenic threats to both the wetlands. The more intense agricultural practices and waste discharge was closely associated with higher phosphate concentration and low level of dissolved oxygen (DO). The biological analysis reveals a notable reduction of the diversity of macroinvertebrates in the downstream direction. Kitto wetland has significantly better MI diversity than Boye (p-value<0.05). Overall, Boye wetland was relatively more polluted than Kitto due to intensive pollutant input mostly from the Jimma Town as well as intensive agriculture related practices around the Boye wetland excepts downstream site B3 which was furthest away from human activity. Protecting wetlands from anthropogenic threats is one of the major concerns in developing countries. This can be achieved by creating awareness among people by employing appropriate communication strategies about the importance of wetlands. In addition, intensive surveillance and monitoring programmes could pave the way to address the current catastrophe in the near future.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
We report on three years of continuous monitoring of carbon dioxide (CO 2 ) and methane (CH 4 ) emissions in two contrasting wetland areas of the Okavango Delta, Botswana: a perennial swamp and a seasonal floodplain. The hydrographic zones of the Okavango Delta possess distinct attributes (e.g. vegetation zonation, hydrology) which dictate their respective greenhouse gas (GHG) temporal emission patterns and magnitude. The perennial swamp was a net source of carbon (expressed in CO 2 -eq units), while the seasonal swamp was a sink in 2018. Despite differences in vegetation types and lifecycles, the net CO 2 uptake was comparable at the two sites studied in 2018/2020 (−894.2 ± 127.4 g m −2 yr −1 at the perennial swamp, average of the 2018 and 2020 budgets, and −1024.5 ± 134.7 g m −2 yr −1 at the seasonal floodplain). The annual budgets of CH 4 were however a factor of three larger at the permanent swamp in 2018 compared to the seasonal floodplain. Both ecosystems were sensitive to d...
PHYSICAL HYDROLOGY OF THE MIDDLE MOHLAPITSI WETLAND, CAPRICORN DISTRICT, SOUTH AFRICA
Anthropogenic intervention in wetlands water dynamics is thought to have created significant changes in water table fluctuations in the Middle Mohlapitsi Wetland. For example, clearing or drainage of wetlands can lead to losses of stored organic carbon (C) to atmospheric carbon dioxide (CO2). By doing this, wetlands mitigate climate change. Changes from flooded to drained conditions in soils stimulate changes from aquatic to terrestrial vegetation and decrease the algal contribution to total primary production. The objective of this paper is to analyse and quantify the dynamics of water generation and retention within the wetland. The study involved both fieldwork and laboratory analyses. Twenty (20) piezometers made from 65 mm diameter PVC tubes were installed along three transects namely T4, T5 and T6. T4 is the widest transect (596.50m); with nine piezometers that were kept in place until the end of 2012. T5 is the second widest transect (450.70 m) with a total of eight piezometers and is located in the left bank of the river. Among this group of transects, T6 is the narrowest (198.90m) with only three piezometers. Long-term groundwater table (GWTL) levels were monitored in order to understand water table fluctuations. GWTL fluctuations were measured by an electronic water level recorder and the readings were sent to the authors for desktop analyses. Five funnel-shaped rain gauges were installed in 2005 within the wetland and readings were taken after every rain events until 2012. These readings were used for all calculations. Streamflow readings from 1970 through 2012 were taken from Department of Water Affairs (DWA) weir, located 1 km downstream of the wetland. Between 10/02/2010 and 02/04/2010, the study wetland received some 214 mm of rainwater, and it was observed that GWTLs in all three transect increased. Thereafter, all piezometers did not show any increase or decrease until the end of study period. Statistical analysis showed that there is a significant moderate positive correlation between rainfall and streamflow. However, there is no relationship between rainfall and groundwater. Such complex situations between in groundwater table and rainfall could be caused by rainfall far from the study area. Hydrological processes in the upper and surrounding catchments impact water balance of the wetland under study. Keywords- Mohlapitsi Wetland, water table, transect, piezometer.
Seasonal variations of 11 water quality, namely; pH, TDS, Conductivity, Turbidity, surface water temperature, DO, NH3, PO4, NO3-N, Ca 2+ and Mg 2+ , were assessed in six wetlands, in the dry (December -April) and wet (July-October) seasons for two years, using standard APHA Four major environmental disturbances (farming activities, bushfires, grazing activity, illegal fishing methods) were quantified using Battisti and Salafsky models. Although physical parameters values showed an increase in the dry season compared to the wet season, they were not statistically significant (p>0.05). However, hydro-chemical parameters showed significant seasonal variations (p< 0.05). With the exception of NH3 that was in far excess of the required levels acceptable for aquatic life, in Nabogo and Bunglung sites, the remaining hydro-chemical variables were at tolerable levels necessary for aquatic life. Elevated levels of NH3 and turbidity in these sites were linked to surface run-off from nearby agricultural fields, while turbidity levels showed appreciable levels in Kukobila (395±2.7 NTU) in the wet seasons, compared with the remaining sites. DO levels were lower beyond acceptable limit and partly influenced by surface water temperature. Our results revealed that farming practices and bushfires directly influenced water quality. Consequently, wetlands functional status could degrade further in the near future if current disturbances intensify. Thus managers of wetlands could institute conservation measures, in order to curb future disturbances and enhance.