Nutrients’ distribution and their impact on Pangani River Basin’s ecosystem – Tanzania

Abstract

Surface and groundwater from Pangani River Basin (PRB) were sampled in dry and wet seasons, analysed for dissolved organic and inorganic nutrients (N, P, Si and Urea). There was spatial and seasonal nutrients' variability, with enrichment of dissolved inorganic fractions accumulated from natural and anthropogenic sources. Silicates increased in dry season, whereas nitrate, ammonium, phosphate and urea increased in wet season; except for phosphate, other nutrients increased from upstream to the river mouth. High rate of chemical weathering possibly due to tropical climate and volcanic rocks has caused PRB to have higher concentration of silicates than average freshwater African Rivers. Contribution of PRB to the coast of Indian Ocean was 2.6, 39.0, 45.2, 67.4 and 5444.8 (mol/km/yr) for nitrite, phosphate, ammonium, nitrate and silicates, respectively, which were lower than most of the tropical rivers in the world. Levels of nitrate and phosphate for most of the stations were higher than recommended levels for aquatic ecosystem health. Furthermore, observed hypoxia condition in some stations threatens aquatic life. This study recommends the efficient use of fertilizers to reduce nutrients' uptake into the lakes and rivers so as to meet the recommended level for aquatic and human health.

Impact of Human Activities and Natural Processes on the Seasonal Variability of River Water Quality in Two Watersheds in Lampung, Indonesia

“…Urea fertilizer application in both watersheds is predominantly scheduled during the rainy season, which further adds to the increased NO 3 concentrations in stream water ( Figure 5). Because of less runoff, the concentration of NO 3 was lowest during the dry season in both the Sangharus and Sekampung Hulu Rivers at 0.58 and 0.23 mg/L, respectively, which is in agreement with previous research in Tanzania [42]. Furthermore, lowered NO 3 concentrations during the dry season influence biological activity and denitrification processes, which further reduces NO 3 concentrations [43].…”

Assessment of Water Quality Across Irrigation Schemes: A Case Study of Wetland Agriculture Impacts in Kilombero Valley, Tanzania

“…Change in land use often parallels change in water use, which in turn drives and feeds back to hydro-climatic change on different spatial and temporal scales [2][3][4]. Anthropogenic influences, such as agricultural activities, can degrade surface water quality and make it unsuitable for drinking, sustainable agricultural use, and sustaining biodiversity [5][6][7]. While the expansion from small-scale rain-fed farming to medium-and large-scale irrigation farming has contributed to global food security, it has often been associated with land and water problems [8].…”

“…While the expansion from small-scale rain-fed farming to medium-and large-scale irrigation farming has contributed to global food security, it has often been associated with land and water problems [8]. Specifically, surface water and wet landscapes are susceptible to contamination from agricultural use of chemicals and fertilisers [7,9,10]. Given the role of surface waters in promoting healthy ecosystems and the direct impacts that land use shifts can have, there is need for rapid assessments to detect the With the current trends of shifting from small-scale to medium-and large-scale farming, it becomes crucial to protect natural and seminatural ecosystems from nonsustainable forms of human resource use.…”

“…Increased use of chemicals and excess draining of wetlands for agriculture and the associated irrigation can have impacts not only on aquatic ecosystem, but also on human health. Fertilisers and agrochemicals impact physical-chemical characteristics of surface water and biota at different spatial scales [7,14]. Excess nitrate-N in drinking water, for example, impacts young livestock, pregnant women and infants on a local scale [15].…”

Differences in trophic resources and niches of two juvenile predatory species in three Pangani estuarine zones, Tanzania: stomach contents and stable isotope approaches

“…1 ). The estuary is permanently open, funnel-shaped and part of the Pangani River Basin of about 43,650 km 2 [ 19 , 33 ]. This basin is the third largest in Tanzania.…”