Department of Biophysical, Geoinformation and Physical Land Resources
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Item USING NDVI AND NDWI INDICES TO ASSESS THE SPATIAL, TEMPORAL AND SEASONAL SPREAD OF AQUATIC WEEDS ON LAKE WAMALA, UGANDA (2017–2025).(Kavubu oscar Godfrey, 2026-08-18) kavubu oscar GodfreyABSTRACT Aquatic weed infestation poses a growing threat to the ecological integrity and socio-economic value of shallow tropical lakes in East Africa. Lake Wamala, a shallow lake in central Uganda, supports important fisheries and provides water for surrounding communities, yet its weed dynamics remain poorly quantified. This study assessed the spatial distribution, temporal trends and seasonal dynamics of aquatic weed cover on Lake Wamala using the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI) derived from Sentinel-2 satellite imagery. A dataset of 30,296 pixel-level observations was extracted from 16 ground stations distributed across five regions and seven ecological zone types, spanning three years (2017, 2022 and 2025) and five months (January, February, March, June and September). Descriptive statistics, weed-cover classification using NDVI thresholds, correlation analysis and spatial–temporal trend analysis were performed. Group differences were tested by Welch’s and one-way analysis of variance, and the NDVI–NDWI association by Pearson correlation. The overall mean NDVI was −0.073 (SD = 0.153) and the overall mean NDWI was 0.206 (SD = 0.169), indicating that open water dominates the lake surface. Weed-cover classification showed that 95.2% of pixels were open water or low vegetation, 1.3% moderate vegetation and 3.5% high vegetation (dense weeds). The Southern region emerged as the principal weed hotspot, with the only positive regional mean NDVI (0.012) and the highest proportion of dense-vegetation pixels (12.02%), followed by the Eastern region (4.93%). NDVI declined sharply between 2017 (−0.037) and 2022 (−0.113) before partially recovering by 2025 (−0.072), a pattern attributed to the 2020–2023 La Niña-driven high water levels in the Lake Victoria basin. Seasonally, January (dry season) recorded the least negative NDVI (−0.011) while February (onset of the rains) recorded the most negative (−0.133). NDVI and NDWI were strongly and inversely correlated overall (Pearson r = −0.971), with zone-level coefficients ranging from −0.743 to −0.989, confirming their value as complementary indices for weed mapping. All four group-difference tests — by zone type, region, year and month — were significant at p < .001, with season producing the largest effect (η² = 0.08) and year the smallest (η² = 0.02). The study concludes that aquatic weed infestation on Lake Wamala is not a uniform, lake-wide problem but a spatially concentrated one, driven by nutrient enrichment, shallow bathymetry and sheltered conditions in the Southern and Eastern regions, and modulated by strong inter-annual climate variability. NDVI and NDWI from freely available Sentinel-2 imagery provide a reliable, low-cost basis for routine monitoring. It is recommended that management be spatially targeted on the Southern and Eastern regions, embedded within an adaptive framework that responds to climate variability, supported by an integrated satellite-plus-ground monitoring system, and complemented by catchment nutrient management and community engagement. These measures would allow limited management resources to be directed where they yield the greatest ecological and economic return. Keywords: Lake Wamala; aquatic weeds; NDVI; NDWI; Sentinel-2; remote sensing; weed mapping; eutrophication; adaptive management.Item Councillors block motion to appoint new land board.(daily monitor, 2017-08-28) Kisekka, ChristopherMasaka. Masaka district councilor have rejected the appointment of new land board. The district chairperson, Mr. Jude Mbabaali and some of his executive members found a hard time last week as councilors opposed their move to appoint a new district land board.Item 7 held over elephant tusks(daily monitor, 2017-04-24) Makumbi, CissyLamwo. officials from the office of prime minister have expressed disappointment after residents withdrew land they offered for reset using refugees from south sudan.Item Kitgum official, CAO lock horns over district land title.(daily monitor, 2017-08-23) Komakech, Dan. MichealKitgum. Kitgum district's senior land officer Mathew Otto is holding on to a land title the district needs to pave way for the construction of market in Orom sub-county.Item Gold mining: Artisan shum borax for mercury's gains(New Vision, 2017-08-31) Kayiwa, EdwardJustine Nantumbwe kneels under a tent at the foot of Kayonza hills in Mubende district trying to seperate gold from the mud with drops of mercury using two plastic basins.Item Uganda can extract golden tips from Rwandan mines(New Vision, 2017-07-06) Odyek, JohnWhereas the Ugandan artisanal miners rely on rudementary, risky methods to get the precious metals, in Rwanda the sector has long been formalised. Uganda's artisan miners do not have much going for them. They live in deplorable conditions and are at the bottom of the food chain as middlemen and mineral exporters enjoy the profit.Item Houses pop up at Nakawa-Naguru estates.(Sunday Vision, 2017-07-23) Kiwawulo, ChrisShock has gripped ex-tenants of Nakawa-Naguru estates after it emerged that the land that had been awarded to UK company, Opet Prime properties for redevelopment into satallitc town has been grabbed by mafias.Item Suspected Karimojong attack Katakwi farmers(New Vision, 2018-04-05) Alomu, EmmanuelSuspected Karimojong from Napak district on Monday attacked and injured about nine people in Amuturunyo village, Obwobwo parish, Ongongoja sub-county in Katakwi district. An LC3 chairperson is said to have been the ringleader in the attacks sparked off by a disagreement over land boundaries.Item Shs3.5b needed for research on fish(New Vision, 2018-04-09) Natambi, AgnesThe National Agriculture Fisheries Research Institute (NaFIRRI) requires an annual budget of about sh3.5b to adequately research on fish in Ugandan waters.Item Katureebe, neighbour clash over access road(Daily Monitor, 2018-02-07) Wesaka, AnthonyA retired banker claims his attempts to repossess part of his prime land turned into an access road to the chief Justice's official residence have been futile.Item Bishop promotes fish farming(Daily Monitor, 2018-03-10) Okello, Warom FelixArua diocese has turned to promoting fish farming in an effort to put an end to malnutrition in families.Item Government moves to boost fish stock in face of extinction(Daily Monitor, 2018-05-09) Okello, Warom FelixNARO has started training and helping farmers to establish fish farms.Item Buvuma fish farmers blame OWC for losses(Daily Monitor, 2018-05-07) Ssebwami, DennisComplaint. They say the fingerlings supplied are not growing despite feeding them.