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Hydrology

Volume XVI |

Aquifer Mapping and Characterization in the Complex Transition Zone of Ijebu Ode, Southwestern Nigeria

Abstract: Vertical electrical soundings (VES) and geophysical logs were employed to map and characterize the aquifer units in the Northwestern zone of Ijebu Ode, Southwestern Nigeria with a view to appraise the groundwater potential of the area. Sixteen Schlumberger soundings (VES) having maximum current electrode separation of 900 m were acquired and interpreted through partial curve matching and computer iteration. Gamma ray and resistivity logs acquired in a drilled hole were interpreted for aquifer characteristics. All but one sounding (VES 9), indicated signatures that are diagnostic of poor hydrogeological characteristics. Four layers were interpreted within 80 m depth. The first layer composed of topsoil (dry clay) which ranges in thickness from 0.8 to 1.5 m. Sandy clay (53 – 1895 Ωm) with varying thickness (0.8 – 34.5 m) constitute the second layer. Thick sand (2.4 – 55.3 m) having high resistivity (1208 – 7350 Ωm) make up the third layer. Resistive basement (3155 – 39529 Ωm) occurring at depth of 3 – 63 m constitute the fourth layer. The low resistivity sand (1023 Ωm) located beneath VES 9 was identified to be the saturated aquifer.  The saturated aquifer has 8 – 10% clay content and 40% porosity. The aquifer is 100% saturated with fresh water having resistivity of 122 Ωm and TDS value of 53 ppm. This study showed that the area was of low groundwater potential and highlights the significance of combined surface and subsurface geophysical investigations for groundwater in area where groundwater occurrence is erratic.

Volume XV |

A Special Issue: Hydrological Behaviour in Small Basins Under Changing Conditions

Abstract: The present paper aim to overview on the Euromediterranean Network of Experimental and Representative Basins conference – ERB 2016. The 16th Biennial Conference ERB was held 5–8 September 2016 in Bucharest, Romania, and was hosted by National Institute of Hydrology and Water Management. The conference program focused on the theme “Hydrological behaviour in small basins under changing conditions”. The conference was followed by a field work on microscale hydrologic monitoring of water balance elements in Voinești Experimental Basin.
This special issues of Forum geografic/Geographical Phorum – Geographical studies and environment protection research (indexing in international databases) includes selected works – contained a variety of hydrology subjects – presented at the Euromediterranean Network of Experimental and Representative Basins conference. All published papers are assigned to Digital Object Identifier (DOI).

Volume XV |

Field Assessment of Soil Water Repellency Using Infrared Thermography

Abstract: This study aimed to evaluate the applicability of an infrared thermography technique relying on cooling the soil surface with cold water for assessing soil water repellency (SWR) severity under field conditions.
This study is a follow-up of earlier exploratory small-scale laboratory tests, where SWR spatial variability was mapped and repellent areas could be clearly detected on the thermal imaging due to their higher temperatures, thus distinguishing them from the remaining wettable areas.
Field tests were carried out, where both natural and artificial SWR were mapped through thermal imaging, using a portable infrared video camera. Cold water was used to create a temperature gradient on the soil surface in order to assess SWR.
Naturally repellent soils were found in a pine and eucalyptus forest and artificial SWR was induced with a waterproofing spray.
The molarity of an ethanol droplet (MED) test was used to measure both natural and artificial SWR severity.
The technique was, in overall terms, successful in mapping SWR spatial variability, distinguishing repellent from wettable areas as well as distinguishing different levels of SWR severity.
Only extensive testing can, ultimately, validate the technique and reveal its suitability in different field conditions (e.g., surface roughness, surface cover, spatial scale).

Volume XV |

Effect of changes in groundwater levels on selected wetland plant communities

Abstract: Wetland areas maintain a high level of moisture at all times and experience flooding at regular intervals. High groundwater levels help create wetland areas, as does a relative lack of surface water loss. The paper bases on the hypothesis that wetland areas are characterized by seasonally high water levels and drought. These changes in water content markedly affect the presence of rare plant communities. The purpose of this paper is to determine the effect of changes in the level of groundwater on selected plant communities in wetland areas. The paper also aims to determine if any other determinants affect these plant communities: (1) relief, (2) climate conditions (precipitation, temperature), (3) human impact. Furthermore, the paper provides a detailed hydrographic analysis of wetland areas including information on water migration pathways, water recharge systems, and sources of water loss. The study area consists of Piaśnickie Łąki – a protected natural area in northern Poland, close to the Baltic coastline. It is also a designated “Nature 2000” area, and it is abundant in rare plant communities such as reed grass (Molinietum medioeuropaeum), which thrives in variable moisture areas. The majority of the research work consisted of literature analysis and fieldwork, which included the installation of a groundwater monitoring system, groundwater and surface water level gauging, and discharge gauging for larger streams found adjacent to the study area. The fieldwork was done in the period 2014 – 2015. The collected research data indicate that groundwater levels did vary during the study period. These conditions helped produce a high rate of plant growth and an increased rate of evapotranspiration across the surface of the study area, which then helped decrease the level of groundwater. One basic condition for the functioning of variable-moisture reed grass communities (Molinietum medioeuropaeum) is a specific pattern of variability in groundwater levels. Small depressions in the studied nature reserve offer the best conditions for the occurrence of reed grass communities.

Volume XV |

SWAT Model Application for Simulating Nutrients Emission from an Agricultural Catchment in Ukraine

Abstract: For the first time in Ukraine, a process-based watershed model SWAT was applied for the analysis of a surface water body contamination by nitrogen and phosphorus compounds. The model was applied in a small Holovesnya River Catchment (area 30.4 km2) located in the forest zone of Ukraine on the territory of the Desna water-balance station. The model run was in daily step for years 1985−1988, 2007, 2009, 2010, 2012. The calibration and validation within SWAT-CUP showed good results for streamflow (NS, R2 > 0.6, PBIAS < 4%), acceptable for nitrogen and phosphorus loads (NS > 0.6, RSR < 0.6, PBIAS < 43%). Streamflow and removal of nitrogen and phosphorus mineral compounds were to estimate the dependence of nutrient wash-off on the amount and practice of fertilizing were evaluated to provide recommendations for agricultural management. Increase of the amount of fertilizer results in the reduction of its efficiency. Divided application of fertilizer leads to the nitrate wash-off reduction by 66%.