| 1. |
- Bouksila, F., et al.
(författare)
-
Electromagnetic induction prediction of soil salinity and groundwater properties in a Tunisian Saharan oasis
- 2012
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 57:7, s. 1473-1486
-
Tidskriftsartikel (refereegranskat)abstract
- Electromagnetic induction measurements (EM) were taken in a saline gypsiferous soil of the Saharan-climate Fatnassa oasis (Tunisia) to predict the electrical conductivity of saturated soil extract (ECe) and shallow groundwater properties (depth, Dgw, and electrical conductivity, ECgw) using various models. The soil profile was sampled at 0.2 m depth intervals to 1.2 m for physical and chemical analysis. The best input to predict the log-transformed soil salinity (lnECe) in surface (0-0.2 m) soil was the EMh/EMv ratio. For the 0-0.6 m soil depth interval, the performance of multiple linear regression (MLR) models to predict lnECe was weaker using data collected over various seasons and years (R-a(2) = 0.66 and MSE = 0.083 dS m(-1)) as compared to those collected during the same period (R-a(2) = 0.97, MSE = 0.007 dS m(-1)). For similar seasonal conditions, for the Dgw-EMv relationship, R-2 was 0.88 and the MSE was 0.02 m for Dgw prediction. For a validation subset, the R-2 was 0.85 and the MSE was 0.03 m. Soil salinity was predicted more accurately when groundwater properties were used instead of soil moisture with EM variables as input in the MLR.
|
|
| 2. |
- Davies, J., et al.
(författare)
-
Comparison of a Multiple Interacting Pathways model with a classical kinematic wave subsurface flow solution
- 2012
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 57:2, s. 203-216
-
Tidskriftsartikel (refereegranskat)abstract
- A discrete random particle representation of flow processes on shallow hillslopes is compared with solutions of the classical kinematic wave representation. The discrete Multiple Interacting Pathways (MIPs) model has the potential to represent the effects of complex heterogeneities and preferential flow pathways. It is shown that, under shared assumptions, the MIPs model can produce equivalent flow predictions to a standard kinematic wave realization. The MIPs model is then used to further explore the relationship between celerity and water velocity by introducing a velocity distribution, which represents the range of possible flow pathways, and therefore is representative of the nature of heterogeneity (or lack of it within a homogeneous case) within the subsurface. It is shown that, whilst flux constraints can be satisfied with a distribution of flow velocities, it can result in changes to the hydrograph. Multiple pathways also have an influence on the residence times for input increments, output increments and storage in the system.
|
|
| 3. |
- Di Baldassarre, Giuliano, et al.
(författare)
-
Flood-plain mapping : a critical discussion of deterministic and probabilistic approaches
- 2010
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 55:3, s. 364-376
-
Tidskriftsartikel (refereegranskat)abstract
- Different methodologies for flood-plain mapping are analysed and discussed by comparing deterministic and probabilistic approaches using hydrodynamic numerical solutions. In order to facilitate the critical discussion, state-of-art techniques in the field of flood inundation modelling are applied to a specific test site (River Dee, UK). Specifically, different flood-plain maps are derived for this test site. A first map is built by applying an advanced deterministic approach: use of a fully two-dimensional finite element model (TELEMAC-2D), calibrated against a historical flood extent, to derive a 1-in-100 year flood inundation map. A second map is derived by using a probabilistic approach: use of a simple raster-based inundation model (LISFLOOD-FP) to derive an uncertain flood extent map predicting the 1-in-100 year event conditioned on the extent of the 2006 flood. The flood-plain maps are then compared and the advantages and disadvantages of the two different approaches are critically discussed.
|
|
| 4. |
- Di Baldassarre, Giuliano, et al.
(författare)
-
Future hydrology and climate in the River Nile basin : a review
- 2011
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 56:2, s. 199-211
-
Tidskriftsartikel (refereegranskat)abstract
- A critical discussion of recent studies that analysed the effects of climate change on the water resources of the River Nile Basin (RNB) is presented. First, current water-related issues on the RNB showing the particular vulnerability to environmental changes of this large territory are described. Second, observed trends in hydrological data (such as temperature, precipitation, river discharge) as described in the recent literature are presented. Third, recent modelling exercises to quantify the effects of climate changes on the RNB are critically analysed. The many sources of uncertainty affecting the entire modelling chain, including climate modelling, spatial and temporal downscaling, hydrological modelling and impact assessment are also discussed. In particular, two contrasting issues are discussed: the need to better recognize and characterize the uncertainty of climate change impacts on the hydrology of the RNB, and the necessity to effectively support decision-makers and propose suitable adaptation strategies and measures. The principles of a code of good practice in climate change impact studies based on the explicit handling of various sources of uncertainty are outlined.
|
|
| 5. |
- Issa, Issa E., et al.
(författare)
-
Sedimentation and new operational curves for Mosul Dam, Iraq
- 2013
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 58:7, s. 1456-1466
-
Tidskriftsartikel (refereegranskat)abstract
- Mosul dam is one of the biggest hydraulic structures in Iraq. Its storage capacity is 11.11×109 m3 at a maximum operation level 330 m of a.s.l. The dam became operational in 1986 and no survey has been conducted to determine its storage capacity and establish new operational curves since this date. In this research topographic map scale 1: 50000 dated 1983 was converted to triangulated irregular network (TIN) format using the Arc/GIS program to evaluate the operational curves. Then the reservoir was surveyed in 2011 to establish the reduction in its storage capacity and to develop new operational curves. The results indicated that the reduction in the storage capacity of the reservoir was 14.73%. This implies that the rate of sedimentation within the reservoir was 45.72×106 m3.yr-1. The results indicated that most of the sediment was deposited within the upper zone of the reservoir where the River Tigris enters the reservoir.
|
|
| 6. |
- Jebari, Sihem, et al.
(författare)
-
Historical aspects of soil erosion in the Mejerda catchment, Tunisia
- 2012
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 57:5, s. 901-912
-
Tidskriftsartikel (refereegranskat)abstract
- Agricultural use and related water erosion leads to significant changes in the sedimentological and hydrological characteristics of watersheds and thus means negative consequences for rural development. This research work aimed at putting present-day soil erosion of the important Mejerda catchment in to a historical context. The catchment of wadi Mejerda in northern Tunisia has experienced soil erosion due to weather and human impact during thousands of years. We used historical texts and results from archeological research that go back to 1000 B.C. as well as data collected during the last century. Soil erosion from different types of agricultural landscape management was analyzed together with information on the soils’ production potential, hydrographical network, and flood frequency. The results showed that water erosion has increased the hydrographic network by 65 km and increased the deltaic plain as much as 15 km2/century. The soil productivity has, however, also decreased significantly. Moreover, due to river choking, the number of overflowing occurrences has multiplied over the last century. Finally, it is shown that water erosion follows a specific cycle of degradation throughout the watershed. These findings could be considered for better water and soil management in the context of semiarid areas.
|
|
| 7. |
- Jebari, Sihem, et al.
(författare)
-
Spatial soil loss risk and reservoir siltation in semi-arid Tunisia
- 2010
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 55:1, s. 121-137
-
Tidskriftsartikel (refereegranskat)abstract
- Soil erosion vulnerability and extreme rainfall characteristics over the Mediterranean semi-arid region of Tunisia are crucial input for estimation of siltation rate in artificial reservoirs. A comprehensive high-resolution database on erosive rainfall, together with siltation records for 28 small reservoirs, were analysed for this region, the Tunisian Dorsal (the easternmost part of the Atlas Mountains). The general life-span of these reservoirs is only about 14 years. Depending on the soil degradation in the different catchments, the corresponding reservoirs display a wide range of soil erosion rates. The average soil loss was 14.5 t ha(-1) year(-1) but some catchments display values of up to 36.4 t ha(-1) year(-1). The maximum 15-min duration rainfall intensity was used to determine the spatial distribution of rainfall erosivity. The northwestern parts of the Tunisian Dorsal display the most extreme rainfall erosivity. Spatial erosion patterns are to some extent similar; however, they vary greatly according to their location in the "soil degradation cycle". This cycle determines the soil particle delivery potential of the catchment. In general, the northwestern parts of the Dorsal display modest soil erosion patterns due to the already severely degraded soil structure. Here, the soil surface is often the original bedrock. However, the greatest soil erosion occurs in the mid-eastern parts of the Dorsal, which represents the "degradation front". The latter corresponds to the area with highest erosion, which is continuously progressing westward in the Dorsal. The large variation between the erosive rainfall events and the annual soil loss rates was explained by two important factors. The first relates to the soil degradation cycle. The second factor corresponds to the degradation front with the highest soil loss rates. At present this front is located at 300 m altitude and appears to be moving along an 80-km westward path starting from the east coast. A better understanding of the above can be used to better manage soils and soil covers in the Tunisian Dorsal area and, eventually, to decrease the soil erosion and reservoir siltation risk.
|
|
| 8. |
- Kizza, Michael, et al.
(författare)
-
Modelling catchment inflows into Lake Victoria : uncertainties in rainfall-runoff modelling for the Nzoia River
- 2011
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 56:7, s. 1210-1226
-
Tidskriftsartikel (refereegranskat)abstract
- Climate and soil characteristics vary considerably around the Lake Victoria basin resulting in high spatial and temporal variability in catchment inflows. However, data for estimating the inflows are usually sparsely distributed and error-prone. Therefore, modelled estimates of the flows are highly uncertain, which could explain early difficulties in reproducing the lake water balance. The aim of this study was to improve the estimates of catchment flow to Lake Victoria. The WASMOD model was applied to the Nzoia River, one of the major tributaries to Lake Victoria. Uncertainty was assessed within the GLUE framework. During calibration, log-transformation was performed on both simulated and observed flows. The results showed that, despite its simple structure, WASMOD produces acceptable results for the basin. For a Nash-Sutcliffe efficiency (NS) threshold of 0.6, the percentage of observations bracketed by simulations (POBS) was 74%, the average relative interval length (ARIL) was 0.93, and the maximum NS value was 0.865. The residuals were shown to be homoscedastic, normally distributed and nearly independent. When the NS threshold was increased to 0.8, POBS decreased to 54% with an improvement of ARIL to 0.49, highlighting the effect of the subjective choice of likelihood threshold.
|
|
| 9. |
- Koussis, A. D., et al.
(författare)
-
Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: Application to the Akrotiri Basin and Aquifer, Cyprus
- 2010
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 55:7, s. 1234-1245
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the general methodology for an intensive development of coastal aquifers, described in a companion paper, through its application to the management of the Akrotiri aquifer, Cyprus. The Zakaki area of that aquifer, adjacent to Lemessos City, is managed such that it permits a fixed annual agricultural water demand to be met, as well as and a fraction of the water demand of Lemessos, which varies according to available surface water. Effluents of the Lemessos wastewater treatment plant are injected into the aquifer to counteract the seawater intrusion resulting from the increased pumping. The locations of pumping and injection wells are optimized based on least-cost, subject to meeting the demand. This strategy controls sea intrusion so effectively that desalting of only small volumes of slightly brackish groundwater is required over short times, while ∼2.3 m3 of groundwater is produced for each 1 m3 of injected treated wastewater. The cost over the 20-year period 2000-2020 of operation is ∼40 M€ and the unit production cost of potable water is under 0.2 €/m3. The comparison between the deterministic and stochastic analyses of the groundwater dynamics indicates the former as conservative, i.e. yielding higher groundwater salinity at the well. The Akrotiri case study shows that the proposed aquifer management scheme yields solutions that are preferable to the widely promoted seawater desalination, also considering the revenues from using the treated wastewater for irrigation.
|
|
| 10. |
- Koussis, A. D., et al.
(författare)
-
Cost-efficient management of coastal aquifers via recharge with treated wastewater and desalination of brackish groundwater: General framework
- 2010
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 55:7, s. 1217-1233
-
Tidskriftsartikel (refereegranskat)abstract
- Semi-arid coastal zones often suffer water-stress, as water demand is high and markedly seasonal, due to agriculture and tourism. Driven by scarcity of surface water, the communities in semi-arid coastal regions turn to aquifers as prime water source; but intensive exploitation of coastal aquifers causes seawater intrusion, which degrades the quality of groundwater. The cost-efficient and sustainable development of coastal aquifers can be achieved through a holistic management scheme which combines two non-traditional water sources: (a) saltwater, to be treated to the desired quality, and (b) wastewater, to be re-claimed to augment aquifer recharge for control of seawater intrusion, and also to meet certain demands. This management scheme is based on the idea that it is cost-advantageous to: (i) desalt brackish groundwater, instead of seawater, as the former requires far less energy, and (ii) to re-use wastewater at only the differential cost to any treatment already practiced. In this paper, we present the general framework of the proposed management scheme, and a decision aid tool (DAT) which has been developed to assist decision makers to explore the scheme's decision space. The DAT uses cost as optimization criterion to screen various management scenarios, via modelling of the dynamic natural-engineered system behaviour, and identifies those cost-efficient ones that meet the water demand and achieve aquifer protection.
|
|
