Comparative Assessment of Emitter Clogging under Fishpond and Swamp Water Sources for Smallholder Drip Irrigation Systems. A Case Study of Limoto Wetland Restoration Site, Pallisa District, Uganda
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Date
2026
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Busitema University
Abstract
Emitter clogging is the leading operational constraint of drip irrigation systems when low-quality
surface water is used. At the Limoto Wetland Restoration Site, Pallisa District, Uganda, fishpond
water (FW) and swamp water (SW) are alternately supplied through a solar-powered drip system
serving smallholder vegetable farmers. This study comparatively assessed emitter clogging under
both sources over a 90-day field experiment, addressing water quality characterization, emitter
discharge performance, deposit characterization, and source-specific engineering mitigation. FW
posed Severe clogging risk across all parameter categories: total suspended solids (185 mg/L),
turbidity (126 NTU), iron (1.66 mg/L), calcium (82 mg/L), phosphate (6 mg/L), total coliforms
(1.6 × 10⁶ CFU/100 mL), and algal biomass (85 µg/L), all substantially exceeding SW values and
FAO risk thresholds. Field monitoring revealed a clear divergence: FW emitter discharge declined
from 1.599 L/h to 1.025 L/h, yielding a clogging rate of 35.90% surpassing the ISO failure
threshold of 25%. SW emitters recorded only 20.64% clogging, remaining within acceptable
operational limits throughout. Welch's t-test confirmed highly significant differences at every
monitoring interval (t = 29.07, df = 12, p = 1.71 × 10⁻¹²). Deposit characterization via SEM, loss
on ignition, and UV-Vis spectrophotometry revealed contrasting clogging regimes. FW deposits
were dominated by a biological fraction (48%), driven by a synergistic EPS-iron hydroxide ochre
biofilm. SW deposits were predominantly physical (54%), comprising porous granular silt despite
greater deposit mass a phenomenon termed the "Clogging Paradox." The standard 130-µm disc
filter was found inadequate for both sources. Recommended mitigation includes sand media
filtration with periodic shock chlorination (10-20 mg/L) and acid injection for FW, and
sedimentation basins with bi-weekly lateral flushing for SW. These findings provide actionable,
context-specific engineering guidance for improving smallholder drip irrigation sustainability at
Limoto Wetland Restoration Site.
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Research Dissertation
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Citation
Etum S.(2026). Comparative Assessment of Emitter Clogging under Fishpond and Swamp Water Sources for Smallholder Drip Irrigation Systems. A Case Study of Limoto Wetland Restoration Site, Pallisa District, Uganda. Busitema University