scholarly journals Implications of deep drainage through saline clay for groundwater recharge and sustainable cropping in a semi-arid catchment, Australia

2011 ◽  
Vol 8 (6) ◽  
pp. 10053-10093
Author(s):  
W. A. Timms ◽  
R. R. Young ◽  
N. Huth
Keyword(s):  
Potential Evapotranspiration ◽  
Shallow Groundwater ◽  
Flood Plain ◽  
Critical Issue ◽  
Continuous Cropping ◽  
Deep Drainage ◽  
Groundwater Levels ◽  
Salt Leaching ◽  
Perennial Vegetation ◽  
Semi Arid

Abstract. The magnitude and timing of deep drainage and salt leaching through clay soils is a critical issue for dryland agriculture in semi-arid regions (<500 mm yr−1 rainfall), such as parts of Australia's Murray-Darling Basin (MDB). In this unique study, hydrogeological measurements and estimations of the historic water balance of crops grown on overlying Grey Vertosols were combined to estimate the contribution of deep drainage below crop roots to recharge and salinization of shallow groundwater. Soil sampling at two sites on the alluvial flood plain of the Lower Namoi catchment revealed significant peaks in chloride concentrations at 0.8–1.2 m depth under perennial vegetation and at 2.0–2.5 m depth under continuous cropping indicating deep drainage and salt leaching since conversion to cropping. Total salt loads of 91–229 t ha−1 NaCl equivalent were measured for perennial vegetation and cropping, with salinity to ≥10 m depth that is not detected by shallow soil surveys. Groundwater salinity varied spatially from 910 to 2430 mS m−1 at 21 to 37 m depth (N = 5), whereas deeper groundwater was less saline (290 mS m−1) with use restricted to livestock and rural domestic supplies in this area. The Agricultural Production Systems Simulator (APSIM) software package predicted deep drainage of 3.3–9.5 mm yr−1 (0.7–2.1% rainfall) based on site records of grain yields, rainfall, salt leaching and soil properties. Predicted deep drainage was highly episodic, dependent on rainfall and antecedent, and over a 39 yr period was restricted mainly to the record wet winter of 1998. During the study period, groundwater levels were unresponsive to major rainfall events (70 and 190 mm total), and most piezometers at about 18 m depth remained dry. In this area, at this time, recharge negligible due to low rainfall and large potential evapotranspiration, transient hydrological conditionsafter changes in land use and a thick clay dominated vadose zone. This is in contrast to regional groundwater modelling that assumes annual recharge of 0.5% of rainfall. Importantly, it was found that leaching from episodic deep drainage could not cause discharge of saline groundwater in the area, since the water table was several meters below the incised river bed.

scholarly journals Implications of deep drainage through saline clay for groundwater recharge and sustainable cropping in a semi-arid catchment, Australia

2012 ◽  
Vol 16 (4) ◽  
pp. 1203-1219 ◽  
Author(s):  
W. A. Timms ◽  
R. R. Young ◽  
N. Huth
Keyword(s):  
Potential Evapotranspiration ◽  
Shallow Groundwater ◽  
Flood Plain ◽  
Critical Issue ◽  
Continuous Cropping ◽  
Deep Drainage ◽  
Groundwater Levels ◽  
Salt Leaching ◽  
Perennial Vegetation ◽  
Semi Arid

Abstract. The magnitude and timing of deep drainage and salt leaching through clay soils is a critical issue for dryland agriculture in semi-arid regions (<500 mm yr−1 rainfall, potential evapotranspiration >2000 mm yr−1) such as parts of Australia's Murray-Darling Basin (MDB). In this rare study, hydrogeological measurements and estimations of the historic water balance of crops grown on overlying Grey Vertosols were combined to estimate the contribution of deep drainage below crop roots to recharge and salinization of shallow groundwater. Soil sampling at two sites on the alluvial flood plain of the Lower Namoi catchment revealed significant peaks in chloride concentrations at 0.8–1.2 m depth under perennial vegetation and at 2.0–2.5 m depth under continuous cropping indicating deep drainage and salt leaching since conversion to cropping. Total salt loads of 91–229 t ha−1 NaCl equivalent were measured for perennial vegetation and cropping, with salinity to ≥ 10 m depth that was not detected by shallow soil surveys. Groundwater salinity varied spatially from 910 to 2430 mS m−1 at 21 to 37 m depth (N = 5), whereas deeper groundwater was less saline (290 mS m−1) with use restricted to livestock and rural domestic supplies in this area. The Agricultural Production Systems Simulator (APSIM) software package predicted deep drainage of 3.3–9.5 mm yr−1 (0.7–2.1% rainfall) based on site records of grain yields, rainfall, salt leaching and soil properties. Predicted deep drainage was highly episodic, dependent on rainfall and antecedent soil water content, and over a 39 yr period was restricted mainly to the record wet winter of 1998. During the study period, groundwater levels were unresponsive to major rainfall events (70 and 190 mm total), and most piezometers at about 18 m depth remained dry. In this area, at this time, recharge appears to be negligible due to low rainfall and large potential evapotranspiration, transient hydrological conditions after changes in land use and a thick clay dominated vadose zone. This is in contrast to regional groundwater modelling that assumes annual recharge of 0.5% of rainfall. Importantly, it was found that leaching from episodic deep drainage could not cause discharge of saline groundwater in the area, since the water table was several meters below the incised river bed.

Accumulation of soil carbon under zero tillage cropping and perennial vegetation on the Liverpool Plains, eastern Australia

Soil Research ◽  
2009 ◽  
Vol 47 (3) ◽  
pp. 273 ◽  
Author(s):  
R. R. Young ◽  
B. Wilson ◽  
S. Harden ◽  
A. Bernardi
Keyword(s):  
Field Experiment ◽  
Soil Carbon ◽  
Cropping Systems ◽  
Annual Rainfall ◽  
Continuous Cropping ◽  
Zero Tillage ◽  
Accumulation Rates ◽  
Eastern Australia ◽  
Perennial Vegetation ◽  
Semi Arid

Australian agriculture contributes an estimated 16% of all national greenhouse gas emissions, and considerable attention is now focused on management approaches that reduce net emissions. One area of potential is the modification of cropping practices to increase soil carbon storage. Here, we report short–medium term changes in soil carbon under zero tillage cropping systems and perennial vegetation, both in a replicated field experiment and on nearby farmers’ paddocks, on carbon-depleted Black Vertosols in the upper Liverpool Plains catchment. Soil organic carbon stocks (CS) remained unchanged under both zero tillage long fallow wheat–sorghum rotations and zero tillage continuous winter cereal in a replicated field experiment from 1994 to 2000. There was some evidence of accumulation of CS under intensive (>1 crop/year) zero tillage response cropping. There was significant accumulation of CS (~0.35 Mg/ha.year) under 3 types of perennial pasture, despite removal of aerial biomass with each harvest. Significant accumulation was detected in the 0–0.1, 0.1–0.2, and 0.2–0.4 m depth increments under lucerne and the top 2 increments under mixed pastures of lucerne and phalaris and of C3 and C4 perennial grasses. Average annual rainfall for the period of observations was 772 mm, greater than the 40-year average of 680 mm. A comparison of major attributes of cropping systems and perennial pastures showed no association between aerial biomass production and accumulation rates of CS but a positive correlation between the residence times of established plants and accumulation rates of CS. CS also remained unchanged (1998/2000–07) under zero tillage cropping on nearby farms, irrespective of paddock history before 1998/2000 (zero tillage cropping, traditional cropping, or ~10 years of sown perennial pasture). These results are consistent with previous work in Queensland and central western New South Wales suggesting that the climate (warm, semi-arid temperate, semi-arid subtropical) of much of the inland cropping country in eastern Australia is not conducive to accumulation of soil carbon under continuous cropping, although they do suggest that CS may accumulate under several years of healthy perennial pastures in rotation with zero tillage cropping.

scholarly journals Potential of Shallow Groundwater for Household Level Irrigation Practices in Tahtay Koraro Woreda, Tigray, Northern Ethiopia

2021 ◽  
Vol 13 (1) ◽  
pp. 43-66
Author(s):  
Ermias Hagos ◽  
Amare Girmay ◽  
Tesfamichael Gebreyohannes
Keyword(s):  
Groundwater Recharge ◽  
Large Scale ◽  
Potential Evapotranspiration ◽  
Shallow Groundwater ◽  
Northern Ethiopia ◽  
Groundwater Abstraction ◽  
Groundwater Levels ◽  
Household Level ◽  
Average Value ◽  
Dug Wells

This paper deals with the results of a pilot study conducted to estimate the shallow groundwater resource potential and irrigation capacity at the household level in Tahtay Koraro Woreda, northwestern zone of Tigray, Ethiopia. The potential evapotranspiration and actual evapotranspiration of the study area are estimated to be 1484 mm/year and 814 mm/year respectively. The runoff is approximately calculated to be 280 mm/year and the annual groundwater recharge is estimated to be 29 mm/year. The total annual groundwater abstraction for human, livestock, and irrigation is estimated to be 25 mm/year. It should be noted that the groundwater recharge rate is expected to remain constant while the total annual groundwater discharge is expected to increase from year to year. This relation when projected over a long period may result in a negative groundwater budget which can result in depletion of groundwater (lowering of groundwater levels), reduced baseflow to streams, and deterioration of water quality.  The computed values for hydraulic conductivity of the aquifers range from 1.63 m/day to 7.27 m/day with an average value of 4.9 m/day and transmissivity from 48.9 m2/day to 218.1 m2/day with an average value of 147.14 m2/day. The aquifers in the highly weathered basalt and highly weathered siltstone – sandstone intercalation have transmissivity values ranging from 99 m2/day to 218.1 m2/day with an average value of 157 m2/day and are grouped into the moderate potentiality aquifers category. The aquifers in the slightly weathered and fractured metavolcanics grouped under low potentiality based on the lower transmissivity values (<50 m2/day). The study area has low to moderate groundwater potentiality, hence, large-scale groundwater pumping is not possible. Therefore, the current activity of using hand dug wells for household-level irrigation is the best way of using groundwater for irrigation and other uses as well. Increasing the depth of the existing hand dug wells that are constructed in highly weathered basalt and highly weathered siltstone – sandstone intercalation can also enhance the yield of the hand dug wells. It is recommended to use water-saving irrigation technologies rather than increasing the number of wells. This will also help in increasing the irrigation area. Groundwater recharge enhancement structures such as trenches, percolation ponds, and check dams be constructed in scientifically selected localities to further enhance the groundwater potential.

scholarly journals Temporal dependence of potentiometric levels and groundwater salinity in alluvial aquifer upon rainfall and evapotranspiration

RBRH ◽  
2017 ◽  
Vol 22 (0) ◽  
Author(s):  
Robertson Valério de Paiva Fontes Júnior ◽  
Abelardo Antônio de Assunção Montenegro
Keyword(s):  
Temporal Dynamics ◽  
Potential Evapotranspiration ◽  
Shallow Groundwater ◽  
Temporal Analysis ◽  
Alluvial Aquifer ◽  
Monthly Precipitation ◽  
Groundwater Salinity ◽  
Temporal Dependence ◽  
Time Pattern ◽  
Groundwater Levels

ABSTRACT Rainfall uncertainty and high evapotranspiration rates in the semiarid regions not only play an important impact on surface water scarcity, but interfere on shallow groundwater quantity and quality. The aim of this study was to apply geostatistical methodology to analyze the time dependence of potentiometric levels and groundwater salinity in an intensively monitored alluvial aquifer upon agroclimatological variables, and thus investigate possible monthly and annual correlations. Statistically stable piezometers were considered for the temporal analysis, representing the mean behavior of the whole aquifer. It has been verified that stable piezometers for groundwater levels exhibited temporal dependence of 7 months, similar to the temporal scale of variation for monthly precipitation and potential evapotranspiration, which is consistent to the resulting crossed-semivariogram. Meanwhile, stable piezometers for electrical conductivity showed high uncertainty on temporal dependence scale, which ranged from 3 to 8 months. Thus, rainfall and evapotranspiration alone did not properly explain the temporal dynamics of groundwater salinity. The produced maps successfully identified the long term time pattern of groundwater variation, constituting an important support for water resources evaluation.

scholarly journals The 2010–2015 megadrought in central Chile: impacts on regional hydroclimate and vegetation

2017 ◽  
Vol 21 (12) ◽  
pp. 6307-6327 ◽  
Author(s):  
René D. Garreaud ◽  
Camila Alvarez-Garreton ◽  
Jonathan Barichivich ◽  
Juan Pablo Boisier ◽  
Duncan Christie ◽  
...  
Keyword(s):  
Public Perception ◽  
River Flow ◽  
Central Government ◽  
Potential Evapotranspiration ◽  
Regional Climate ◽  
Climate Scenario ◽  
Annual Rainfall ◽  
Central Chile ◽  
Groundwater Levels ◽  
Semi Arid

Abstract. Since 2010 an uninterrupted sequence of dry years, with annual rainfall deficits ranging from 25 to 45 %, has prevailed in central Chile (western South America, 30–38° S). Although intense 1- or 2-year droughts are recurrent in this Mediterranean-like region, the ongoing event stands out because of its longevity and large extent. The extraordinary character of the so-called central Chile megadrought (MD) was established against century long historical records and a millennial tree-ring reconstruction of regional precipitation. The largest MD-averaged rainfall relative anomalies occurred in the northern, semi-arid sector of central Chile, but the event was unprecedented to the south of 35° S. ENSO-neutral conditions have prevailed since 2011 (except for the strong El Niño in 2015), contrasting with La Niña conditions that often accompanied past droughts. The precipitation deficit diminished the Andean snowpack and resulted in amplified declines (up to 90 %) of river flow, reservoir volumes and groundwater levels along central Chile and westernmost Argentina. In some semi-arid basins we found a decrease in the runoff-to-rainfall coefficient. A substantial decrease in vegetation productivity occurred in the shrubland-dominated, northern sector, but a mix of greening and browning patches occurred farther south, where irrigated croplands and exotic forest plantations dominate. The ongoing warming in central Chile, making the MD one of the warmest 6-year periods on record, may have also contributed to such complex vegetation changes by increasing potential evapotranspiration. We also report some of the measures taken by the central government to relieve the MD effects and the public perception of this event. The understanding of the nature and biophysical impacts of the MD helps as a foundation for preparedness efforts to confront a dry, warm future regional climate scenario.

Continuous cropping under elevated CO2: Differential effects on C4 and C3 crops, soil properties and carbon dynamics in semi-arid alfisols

2016 ◽  
Vol 218 ◽  
pp. 73-86 ◽  
Author(s):  
Ch. Srinivasarao ◽  
Sumanta Kundu ◽  
Arun K. Shanker ◽  
R. Prakash Naik ◽  
M. Vanaja ◽  
...  
Keyword(s):  
Soil Properties ◽  
Elevated Co2 ◽  
Carbon Dynamics ◽  
Continuous Cropping ◽  
Differential Effects ◽  
Semi Arid

scholarly journals The use of groundwater crustacean communities as indicators for aquifers quality in the semi-arid region of north-central Chile

2018 ◽  
Vol 1 ◽  
Author(s):  
Sanda Iepure ◽  
Nicolas Gouin ◽  
Angeline Bertin ◽  
Ana Camacho ◽  
Antonio González-Ramón ◽  
...  
Keyword(s):  
Negative Impact ◽  
Groundwater Resources ◽  
Economic Benefits ◽  
Nutrient Loads ◽  
Groundwater Temperature ◽  
Groundwater Levels ◽  
Water Abstraction ◽  
Over Exploitation ◽  
The Impact ◽  
Semi Arid

Chile has large extensions of arid and semi-arid regions throughout the whole country, where the intensive demands and use of water resources, especially groundwater for irrigations and mining activities, increased dramatically over the last decades. The aquifer depletions due to water abstraction for irrigation and nutrient loads, exert major alterations of water quality, groundwater recharge and the natural renewal rate. All these factors diminish the aquifer value for the users and contribute to the degradation of groundwater as environment and habitat for fauna. This intensive use of groundwater resources in Chile brought to significant social and economic benefits, but their inadequate management resulted in negative environmental, legal and socioeconomic consequences. In this study, we aimed at providing a first assessment of environmental alterations of groundwater ecosystems from agricultural watersheds in northern Chile by specifically evaluating the effects of nitrogen and pesticide loads on groundwater communities and identifing the ecosystem service alterations due to agricultural activities. The study has been performed in a glacial aquifer from Coquimbo region; 250 km north of Santiago de Chile, the floodplain of which is dominated by agriculture (fruits tress, vineyards). Due to low regional precipitations (100-240 mm/year) the aquifer is primarily recharged by snowmelt from the Andean chain and surface runoff. The relative groundwater levels, groundwater temperature, chemical analysis of nitrogen and total phosphorus and pesticide concentrations were examined, along with the evaluation of crustacean biodiversity and spatial distribution pattern. Stygofauna taxonomic richness and the presence of stygobites have been related more to groundwater level stability than to chemical water parameters indicating that over-exploitation has a negative impact on habitat suitability for groundwater invertebrates. Groundwater biota assessment is essential in understanding the impact produced by agriculture activities on groundwater as a resource and as ecosystem, a nexus that becomes more and more widely recognized. The rationale and the preliminary results of this study are summarized in the Suppl. material 1.

scholarly journals Shallow groundwater in sub-Saharan Africa: neglected opportunity for sustainable intensification of small-scale agriculture?

2016 ◽  
Author(s):  
John Gowing ◽  
Geoff Parkin ◽  
Nathan Forsythe ◽  
David Walker ◽  
Alemseged Tamiru Haile ◽  
...  
Keyword(s):  
Groundwater Resources ◽  
Climatic Variability ◽  
Shallow Groundwater ◽  
Sustainable Intensification ◽  
Sub Saharan Africa ◽  
Small Scale ◽  
Groundwater Levels ◽  
Sub Saharan ◽  
Small Scale Irrigation

Abstract. There is a need for an evidence-based approach to identify how best to support development of groundwater for small scale irrigation in sub-Saharan Africa (SSA). We argue that it is important to focus this effort on shallow groundwater resources which are most likely to be used by poor rural communities in SSA. However, it is important to consider constraints, since shallow groundwater resources are likely to be vulnerable to over-exploitation and climatic variability. We examine here the opportunities and constraints and draw upon evidence from Ethiopia. We present a methodology for assessing and interpreting available shallow groundwater resources and argue that participatory monitoring of local water resources is desirable and feasible. We consider possib le models for developing distributed small-scale irrigation and assess its technical feasibility. Because of power limits on water lifting and also because of available technology for well construction, groundwater at depths of 50 m or 60 m cannot be regarded as easily accessible for small-scale irrigation. We therefore adopt a working definition of shallow groundwater as < 20 m depth. This detailed case study in the Dangila woreda in Ethiopia explores the feasibility of exploiting shallow groundwater for small-scale irrigation over a range of rainfall conditions. Variability of rainfall over the study period (9 % to 96 % probability of non-exceedance) does not translate into equivalent variability in groundwater levels and river baseflow. Groundwater levels, monitored by local communities, persist into the dry season to at least the end of December in most shallow wells, indicating that groundwater is available for irrigation use after the cessation of the wet season. Arguments historically put forward against the promotion of groundwater use for agriculture in SSA on the basis that aquifers are unproductive and irrigation will have unacceptable impacts on wetlands and other groundwater-dependent ecosystems appear exaggerated. It would be unwise to generalise from this case study to the whole of SSA, but useful insights into the wider issues are revealed by the case study approach. We believe there is a case for arguing that shallow groundwater in sub-Saharan Africa represents a neglected opportunity for sustainable intensification of small-scale agriculture.

scholarly journals The 2010–2015 mega drought in Central Chile: Impacts on regional hydroclimate and vegetation

2017 ◽  
Author(s):  
René Garreaud ◽  
Camila Alvarez-Garreton ◽  
Jonathan Barichivich ◽  
Juan Pablo Boisier ◽  
Duncan Christie ◽  
...  
Keyword(s):  
River Flow ◽  
Potential Evapotranspiration ◽  
Regional Climate ◽  
Climate Scenario ◽  
Annual Rainfall ◽  
Central Chile ◽  
Groundwater Levels ◽  
Tree Ring Reconstruction ◽  
Neutral Conditions ◽  
Northern Sector

Abstract. Since 2010 an uninterrupted sequence of dry years, with annual rainfall deficits ranging from 25 to 45 %, has prevailed in Central Chile (western South America, 30–38° S). Although intense 1- or 2-year droughts are recurrent in this Mediterranean-like region, the ongoing event stands out because of its longevity and large spatial extent. The extraordinary character of the so-called Central Chile Mega Drought (MD) was established against century long historical records and a millennial tree-ring reconstruction of regional precipitation. The largest MD-averaged rainfall relative anomalies occurred in the northern, semi-arid sector of central Chile but the event was unprecedented to the south of 35° S. ENSO neutral conditions have prevailed since 2011 (but for the strong El Niño 2015) contrasting with La Niña conditions that often accompanied past droughts. The precipitation deficit diminished the Andean snowpack and resulted in amplified declines (up to 90 %) of river flow, reservoir volumes and groundwater levels along central Chile and westernmost Argentina. In some semiarid basins we also found a conspicuous decrease in the runoff-to-rainfall coefficient. A substantial decrease in vegetation productivity occurred in the shrubland-dominated, northern sector, but a mix of greening and browning patches occurred farther south where irrigated croplands and exotic forest plantations dominate. The ongoing warming in central Chile, making the MD one of the warmest 6-year period on record, may have also contributed to such complex vegetation changes by increasing potential evapotranspiration. The understanding of the nature and biophysical impacts of the MD contributes to preparedness efforts to face a dry, warm future regional climate scenario.

Integration of multiple observed and model-derived hydrological variables in landslide initiation threshold models in Rwanda 

2021 ◽  
Author(s):  
Judith Uwihirwe ◽  
Markus Hrachowitz ◽  
Thom Bogaard
Keyword(s):  
Transfer Function ◽  
Potential Evapotranspiration ◽  
Radial Distance ◽  
Data Availability ◽  
Noise Model ◽  
False Alarms ◽  
Operating Characteristics ◽  
Groundwater Levels ◽  
Linear Reservoir ◽  
Landslide Triggering

&lt;p&gt;This study was conducted using data collected from 3 catchments in North-Western region of Rwanda; Kivu, upper Nyabarongo and Mukungwa. We used two parsimonious&amp;#160; models, a transfer function noise time series model and a linear reservoir conceptual model, to simulate groundwater levels using rainfall and potential evapotranspiration as model inputs. The transfer function noise model was identified as the model with great explanatory predictive power to simulate groundwater levels as compared to the linear reservoir model. Hereafter, the modelled groundwater levels were used together with precipitation to explain the landslide occurrence in the studied catchments. These variables were categorized into landslide predisposing conditions which include the standardized groundwater level on the landslide day h&lt;sub&gt;t&lt;/sub&gt; and prior to landslide triggering event h&lt;sub&gt;t-1&lt;/sub&gt; and landslide triggering conditions which include the rainfall event, event intensity and duration.&amp;#160; Receiver operating characteristics curve and area under the curve metrics were used to test the discriminatory power of each landslide explanatory variable. The maximum true skill statistics and the minimum radial distance were used to highlight the most informative hydrological and meteorological threshold levels above which landslide are high likely to occur in each catchment. We will discuss our results of incorporation of groundwater information in the landslide predictions and compare these results with landslide prediction capacity which solely use of precipitation thresholds.Here we focus on at the same time on the practicalities of data availability for day-to-day landslide hazard management, both in terms of missed and false alarms&lt;/p&gt;

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