Spatio-temporal patterns of groundwater depths and soil nutrients in a small watershed in the Ethiopian highlands: Topographic and land-use controls

被引:19
作者
Guzman, Christian D. [1 ,2 ]
Tilahun, Seifu A. [3 ]
Dagnew, Dessalegn C. [4 ]
Zimale, Fasikaw A. [3 ]
Zegeye, Assefa D. [5 ]
Boll, Jan [2 ]
Parlange, Jean-Yves [1 ]
Steenhuis, Tammo S. [1 ,3 ]
机构
[1] Cornell Univ, Dept Biol & Environm Engn, B62 Riley Robb Hall, Ithaca, NY 14853 USA
[2] Washington State Univ, Dept Civil & Environm Engn, Pullman, WA 99164 USA
[3] Bahir Dar Univ, Fac Civil & Water Resources Engn, Bahir Dar, Ethiopia
[4] Bahir Dar Univ, Inst Disaster Risk Management & Food Secur Studie, Bahir Dar, Ethiopia
[5] Amhara Reg Agr Res Inst, Bahir Dar, Ethiopia
关键词
Spatial variability; Topographic controls; Land use; Nutrient depletion; Groundwater table variations; Debre Mawi; RUNOFF PROCESSES; BLUE NILE; DISCHARGE RELATIONSHIPS; FERTILITY MANAGEMENT; DEVELOPING-COUNTRIES; SMALLHOLDER FARMS; STORM RUNOFF; HOT MOMENTS; LAKE TANA; PHOSPHORUS;
D O I
10.1016/j.jhydrol.2017.09.060
中图分类号
TU [建筑科学];
学科分类号
0813 ;
摘要
Soil and water conservation structures, promoted by local and international development organizations throughout rural landscapes, aim to increase recharge and prevent degradation of soil surface characteristics. This study investigates this unexamined relationship between recharge, water table depths, and soil surface characteristics (nutrients) in a small sub-watershed in the northwestern Ethiopian highlands. These highland watersheds have high infiltration rates (mean 70 mm hr(-1) median 33 mm hr(-1)), recharging the shallow unconfined hillslope aquifer with water transport occurring via subsurface pathways down the slope. The perched water tables reflect the subsurface flux and are deep where this flux is rapid in the upland areas (138 cm below surface). Soil saturation and overland flow occur when the subsurface flux exceeds the transport capacity of the soil in the lower downslope areas near the ephemeral stream (19 cm below surface). Land use is directly related to the water table depth, corresponding to grazing and fallowed (saturated) land in the downslope areas and cultivated (unsaturated) land in the middle and upper parts where the water table is deeper. Kjeldahl Total Nitrogen (TN), Bray II available phosphorus (AP), and exchangeable potassium (K+) averages exhibit different behaviors across slope, land use transects, or saturation conditions. TN was moderate to low (0.07% +/- 0.04) in various land uses and slope regions. Bray II AP had very low concentrations (0.25 mg kg(-1) +/- 0.26) among the different slope regions with no significant differences throughout (p > .05). The exchangeable cation (K+, Ca2+, Mg2+) concentrations and pH, however, were greater in non-cultivated (seasonally saturated) lands and in a downslope direction (p < .001, p < .005, p < .05, and p < .005, respectively). These results show that the perched groundwater plays an important role in influencing land use, the amount of water seasonally available for crop growth, and exchangeable cations, but have no clear effect on the concentration of the two primarily applied nutrients in fertilizers (N, P). (C) 2017 Elsevier B.V. All rights reserved.
引用
收藏
页码:420 / 434
页数:15
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