NULIR
The National University of Lesotho Institutional Repository (NULIR) is a digital archive that collects, preserves, and provides open access to the scholarly and intellectual output of the University.
Recent Submissions
IMPACT OF ALTITUDINAL VARIATION ON SELECTED SOIL PROPERTIES AND CARBON DYNAMICS IN THE ALPINE WETLANDS OF LESOTHO
(2025-07-01) Mochala, M
The study entitled, “Impact of Altitudinal Variation on Selected Soil Properties
and Carbon Dynamics in the Alpine Wetlands of Lesotho” was conducted in the on-going
project entitled, “Carbon Modelling and Omics Approaches for Screening of Soil Microbes
for Climate Change Adaptation in the Alpine Wetlands of Lesotho,” initiated in November,
2024. The study was designed in blocks (sub-catchments) with six altitudinal variations
(from 2500 to 3155 m a.s.l), equivalent to alpine wetlands from three sub-catchments
(Senqunyane, Khubelu and Sani) as follows: Khorong (2500-2550 m a.s.l) and Tenesolo
(2552-2600 m a.s.l) in Senqunyane; Khamoqana (2839-2880 m a.s.l) and Khalong-la-
Lichelete (2891-29950 m a.s.l) in Sani; and Lets’eng-la-Likhama (3040-3080 m a.s.l) and
Koting-Sa-ha Ramosetsana (3087-3155 m a.s.l) in Khubelu. Each treatment was replicated
four times. The soil texture was loam to sandy loam across the alpine wetlands. The alpine
wetland soils were slightly acidic and non-saline.
The findings of the study revealed that bulk density (BD) decreased with increasing
altitude 0-15 cm soil depth and was significantly lower (1.08 Mg m-3) in Koting-Sa- ha
Ramosetsana (KSHM) compared to other wetlands. The KSHM also showed significantly
higher infiltration rate (IR) of 2.17 cm hr-1, maximum water holding capacity (MWHC) of
57.51% and saturated hydraulic conductivity (Ksat) of 2.70 cm hr-1 Ksat at 0-15 cm soil depth
whereas, Tenesolo recorded the higher BD and the least IR, MWHC and Ksat. Soil organic
carbon (SOC) and Calcium (Ca) were significantly higher in KSHM and increased with
increasing altitude, except Khorong (KRN) which did not follow this increasing trend, i.e.,
KRN (2500-2550 m a.s.l) was exhibited with higher contents of SOC and Ca. The electrical
conductivity, cation exchange capacity and macronutrients (nitrogen, phosphorus and
potassium) availability of the soil were non-significant.
Soil enzyme activities declined significantly with increase in altitude due to lower
temperatures at higher elevations, limiting microbial activity. The dehydrogenase,
fluorescein di-acetate and β-galactosidase activities were 3.92 and 45.33%, 1.82 and 32.20%
and 9.29 and 15.11% lower in KSHM (3087-3155 m a.s.l) compared to Tenesolo (2552-2600
m a.s.l) and Khorong (2500-2550 m a.s.l), respectively. Higher carbon pools viz., very labile
(CVL), labile (CL), less labile (CLL) and non-labile (CNL) and total organic carbon (TOC) were
recorded under KSHM compared to all other wetlands at varied altitudes. Passive pool of
carbon (CPSV) was dominant over active carbon pool (CACT) with 75–79% contribution
towards TOC. Both CPSV and CACT were higher in KSHM (higher elevation site).
The Soil Quality Index (SQI) was enhanced (42.54% and 42.51%) at both upper
(Koting-sa-ha Ramosetsana) and lower (Khorong) elevation wetlands, indicating that
altitude alone does not fully determine soil quality. Instead, wetland condition, vegetation
cover, and site-specific environmental factors are critical in shaping soil functionality and
regulating carbon processes in alpine wetland ecosystem. Therefore, further research needs
to consider synergistic factors including the slope, topography and soil degradation level in
addition to the altitude.
IMPACT OF SOIL CONDITION, TOPOGRAPHY AND LAND USE ON THE EROSION CHARACTERISTICS OF PHULENG-E-NYANE, HA MANTSEBO: A USLE ANALYSIS THE NATIONAL UNIVERSITY OF LESOTHO
(2025-10-01)
Soil erosion is a natural yet complex process resulting in the detachment and movement of soil by agents including water and wind, often accelerated by anthropogenic activities such as agriculture and land use changes. It threatens soil fertility, agricultural productivity and ecosystem health making its assessment crucial for sustainable land management. In this study, the impact of soil erosion causing factors on the erosion characteristics of Phuleng-e-Nyane Ha-Mantšebo were evaluated using the Universal Soil Loss Equation (USLE) model. A randomized complete block design in a split plot arrangement was employed to assess soil erosion across the area. The main plot consisted of two farming systems, cropland and long-term fallow land. Within each farming system, the subplot factor was the topo-sequence position comprising four levels: summit, shoulder, back-slope and toe-slope. The soil erosion factors used to determine the total soil loss in USLE include, rainfall erosivity index, soil erodibility factor, topographic factor, crop management factor and conservation factor.
Disturbed and undisturbed soil samples were collected, whereby, the disturbed soil samples were collected using soil auger at 30 cm depth and undisturbed soil samples using the core samples. The secondary rainfall data for Moshoeshoe I International Airport was collected from the Lesotho Meteorological services while the slope length was measured using the 100 m fiberglass open reel measuring tape. Google earth was used to look at land use and land cover overtime. Correlation analysis was used to examine the relationship between soil loss and the contributing factors. The localized soil loss prediction model was developed. The total soil loss from study area was calculated at 12.25 Mg ha⁻¹ yr⁻¹ with cropped land contributing about 95.2% of the loss (about 53.7% from the north transect and 41.5% from the southwest transect) while 4.8% was from the long-term fallow land approximately shared equally among the two transects. The stepwise regression analysis revealed that land use is the most influencing factor on soil loss from the area, followed by topography. The study highlights the importance of integrating effective management practices to sustain soil health and reduce erosion hazards.
IMPACTS OF CLIMATE CHANGE ON STREAMFLOW AND HYDROLOGICAL EXTREMES IN THE SOUTH PHUTHIATSANA CATCHMENT, LESOTHO
(2025-10-01) Maphutseng, M
Global climate change is predicted to significantly modify hydrological processes, which will have a big impact on ecosystem sustainability, flood risk, and water availability. Knowing how future climate changes may impact river systems is especially important in southern Africa, where population increase and fluctuating rainfall are already placing a strain on water resources. One such critical system is the South Phuthiatsana catchment, which serves as a vital supply of water for Maseru and the other metropolitan areas.
This study explores how projected climatic shifts may influence streamflow behavior and the occurrence of hydrological extremes within the South Phuthiatsana watershed, an essential source of water for Maseru and surrounding urban communities. Bias-adjusted data from the MPI-ESM1-2-LR global climate model, along with two sample emissions trajectories for the mid-21st century (2041–2080), were used to project climate inputs. Suboptimal performance indicators showed that the process-based model (SWAT+), which was used to simulate streamflow, was not very reliable in capturing historical daily flow patterns. SWAT+ was therefore thought to be insufficient for predicting future hydrological reactions in this context.
A machine learning approach using the XGBoost algorithm was adopted to address this challenge. This data-driven model was trained on bias-corrected climate variables and observed streamflow, providing a more reliable tool for future streamflow prediction. The results from XGBoost revealed substantial and complex hydrological shifts. A consistent warming trend combined with highly variable seasonal precipitation patterns was evident across both emission scenarios. Extreme high flows, represented by the 98th percentile (Q98), are projected to decline by more than 52% compared to historical values, suggesting a reduced risk of flooding. In contrast, low flows are expected to increase dramatically; the 1st percentile (Q1) flow is projected to rise from near-zero values historically to approximately 9.0 m³/s, indicating a significant shift toward more perennial flow conditions.
Mid-range flows (Q25, Q50, and Q75) are also expected to increase substantially, depending on the flow percentile and scenario. While the absolute magnitude of low flows improves, the number
v
of days with historically low flow conditions may still increase during certain months, highlighting a shift in the intra-annual flow variability.
These findings point to a future with altered hydrological regimes in the South Phuthiatsana catchment characterised by diminished flood peaks, elevated baseflows, and more frequent low-flow conditions during critical periods. Despite initial limitations with the process-based model, the machine learning approach provided robust insights that form a valuable foundation for developing adaptive, forward-looking water resource management strategies. These results underscore the need for resilient planning to ensure long-term water security under evolving climate conditions.
SOCIOECONOMIC AND ENVIRONMENTAL DIMENSIONS OF ABANDONED MAQALIKA DAM TO THE SURROUNDING COMMUNITIES IN MASERU, LESOTHO
(2025-10-01) Moloisane. R.M
Maqalika Dam was constructed in 1983 to supply potable water for households and other
uses in Maseru. However, since its abandonment for some time it has suffered
progressive degradation due to pollution, sedimentation, and unregulated urban
encroachment. Against that backdrop, this study examined the socioeconomic and
environmental dimensions of the abandonment of Maqalika Dam in Maseru Lesotho. A
mixed-methods approach comprising household surveys (n=310), key informant
interviews with institutional stakeholders, and field observations was used with
tabulations and content analysis to assess the multifaceted consequences of the dam’s
discontinued use. Findings indicated that over 55% of nearby residents experienced
livelihood disruptions, especially in irrigation, livestock watering, and small-scale fishing.
Environmentally, over 94% of respondents reported pollution, waste dumping, and
eutrophication as prominent challenges which posed risks to public health and aquatic
life. Institutional neglect, rapid urbanization, and intentional pollution were identified as
key drivers of abandonment. Although Metolong Dam now supplies Maseru, the Maqalika
site remains a source of socio-environmental concern. Stakeholders proposed strategies
including pollution source mapping, ecological rehabilitation, and participatory reuse
planning. The study concludes that there is an urgent need for integrated water resource
governance, emphasizing rehabilitation or sustainable repurposing to transform
abandoned urban dams from liabilities into community assets.
EFFECTS OF SEDIMENTATION ON WATER QUALITY IN THE METOLONG RESERVOIR, MASERU, LESOTHO
(2025-07-01) Makhakhe, M
Reservoir sedimentation is a significant environmental challenge affecting the sustainability of water resources, particularly in Lesotho, where soil erosion and land degradation are prevalent due to intensive land–use activities and fragile ecosystems. Metolong Reservoir is a critical water supply for approximately two–thirds of Lesotho's population, challenged with rapid sedimentation which lowers the water quality and threatens the long–term viability of the reservoir, yet no known studies have been done to correlate sedimentation and water quality in the area. This study investigated how sedimentation affects water quality in the Metolong Reservoir by quantifying sediment accumulation in the Metolong Reservoir from 2020 to 2022 and analyzing the impact of sedimentation on key water quality parameters. The study employed historical bathymetric and water quality data (2020–2022), complemented by GIS–based spatial analysis and R statistical modeling to assess the spatial and temporal relationships between sediment deposition and changes in water quality parameters, following the causal–comparative research design. Water quality parameters analyzed were aluminum, Electrical Conductivity (EC), iron, manganese, nitrates, nitrites, phosphates, sulphates, TDS and turbidity. Bathymetric analysis revealed a total sediment accumulation of approximately 1,705,583 m3 (2.68% of reservoir capacity) between 2020 and 2022, concentrated primarily near the reservoir’s middle and towards the dam, resulting in an annual storage loss of 1.34%.Linear regression analysis revealed turbidity as the most significant at (p<0.05).The study also identified turbidity and nitrates as key water quality parameters significantly influenced by sedimentation, with turbidity showing the strongest correlation (r = 0.60) and nitrates showing a moderate correlation (r = 0.2) with sediment volume suggesting possible links with upstream land use and nutrient runoff. There was an increase in nutrients and heavy metals concentration from 2020–2022, indicating a need for intervention, though most water quality parameters were still within WHO and South African water quality standards. The findings confirm that sedimentation negatively affects water quality, underscoring the need for integrated catchment management strategies, including sediment control, land–use planning, and systematic water quality monitoring to safeguard reservoir operations and public health.