Water Productivity Journal
Volume:2 Issue: 4, Autumn 2022

Irrigation water is an expensive and limited resource. Previous studies show that irrigation scheduling can boost efficiency by 20-60%, while improving the water productivity by at least 10%. A key aspect of irrigation scheduling is accurate estimation of crop water use and soil water status, which often require modelling with good information on soil, crop, climate and field management. However, this input information is often highly uncertain. Our study aims to obtain a comprehensive understanding of uncertainties in irrigation scheduling that arise from individual model inputs, from which identifying the key contributor of uncertainty. Our study aims to understand the uncertainty in model-based irrigation scheduling and the key model inputs that contribute to this uncertainty. To achieve this, we first performed a comprehensive literature review to identify the key sources and the expected ranges of uncertainty in individual model inputs. Secondly, a global sensitivity analysis was conducted to quantify the influence of each model input on the total uncertainty of the modelled irrigation scheduling decision, across 14 climatically different locations in Australia.
To achieve this, we used a global sensitivity analysis to assess the relative importance of the uncertainty in each model input to the total uncertainty in output. This analysis focused on the modelled irrigation scheduling (summarized with irrigation amount per day during an irrigation cycle) with a single-bucket soil water balance model following the Food and Agriculture Organisation (FAO). The key input variables required by the model include weather data, crop parameters (i.e., crop coefficient and root depth), soil parameters (plant available water capacity) and management factors (depletion factor).
To define the uncertainty in each model input, we first performed a comprehensive literature review to summarize the key sources of uncertainty in estimating each of these model inputs, and the expected range of uncertainty in the data of each input. Based on these uncertainty ranges, we ran the global sensitivity analysis with the soil water scheduling model. In this analysis, a large number of random samples were drawn for each input variable within its expected range of uncertainty, to produce ensemble simulations of soil water status and thus irrigation scheduling decisions. The total uncertainty in these scheduling decisions were then analysed with respect to that of each input variable, to establish the relative importance of the uncertainty in individual input variables. The sensitivity analysis was performed at 14 climatically different locations in main irrigation districts across Australia to provide a comprehensive understanding of sensitivity.
Our results highlight the crop coefficient as the most important contributor to the total uncertainty in irrigation scheduling simulation, across different climate zones in Australia. The uncertainty in crop coefficient can be potentially reduced by better representation of its spatial and temporal variation, as well as considering alternative approaches such as remote sensing estimates. Our findings are useful to inform the future direction of research to improve irrigation scheduling in Australia. Further, our modelling approach is transferable to other irrigation regions to better understand the uncertainties associated with irrigation scheduling and the key data sources that lead to these uncertainties.

With the development of agricultural technology, it is possible to cultivate crops in winter at the greenhouse facility cultivation complex, and as the crop cultivation period has increased, the use of groundwater has increased. When calculating the amount of groundwater used, the utilization period should be increased according to the cultivation period.
As a result, the groundwater use calculated by the conventional method is applied to the annual use period of 270 days for the whole action and 180 days for the answer action, so the value less than the actual groundwater use for the year is inevitably calculated. Therefore, it is necessary to estimate the irrigation water demand for each crop in consideration of the cultivation period when the groundwater use is calculated in the facility cultivation complex that grows the four-season crops. The purpose of this study was to calculate monthly cultivation crops and cultivation periods through Gwang-ju Meteorological Agency's climate data in South Korea, land cover map, field survey, and residents' survey to estimate the irrigation water demand by crops in the area around Yeongsan River where facility cultivation complex is concentrated.
Based on the results of the calculation of crop evaporation (irrigation water demand) using the crop coefficients presented by the Rural Development Administration and FAO, it was analysed that irrigation water used is 2,114×1000 m3/year for rice, 3,353×1,000 m3/year for field crops, and 6,649×1,000 m3/year for water dropwort. As a result, water dropwort uses irrigation water twice more than field crops. In addition, except for rice, which mainly uses surface water, the difference in usage amount occurred more than twice as compared to the groundwater use calculated by the existing groundwater use method. Therefore, if the facility cultivation complex that grows four seasons of crops water demand calculation method is applied to the irrigation water required by the crops rather than the conventional groundwater usage calculation method, it will not only calculate the exact amount of water but also establish proper water supply measures and facility maintenance. The high agriculture productivity in the command area and poor performance of the irrigation system clearly justifies the role of shallow tubewell has played in the command area. Since the irrigation facility is Agency Managed and O&M of the surface system is carried out by the Government, the investment cost on the tube well and their O&M is entirely contributed by the farmers. The deficit water fulfilled by the tubewell and total cost associated to it is considered to be the total economic loss due to irrigation system inefficiency. Finally, the amount of irrigation water required by the crop during the growth period was calculated by multiplying the monthly crop evaporation amount to the monthly cultivation area. However, it is difficult to calculate the amount of groundwater used as a crop factor by repeating the operation of filling and subtracting water and running water in order to prevent temperature maintenance and dobok (bending) during cultivation. Therefore, in the case of dropwort with a large amount of groundwater, irrigation water demand was separately calculated monthly through field surveys on cultivation area, cultivation period, and cultivation methods and interviews with local residents.
It will be helpful in establishing measures and maintaining water supply facilities. If research on crop factor estimation is activated in the future, it will be possible to more accurately estimate the demand for irrigation water for all crops.

The main objective of this study is to estimate the total economic loss due to inefficient supply of irrigation water in the command area of Nepal Gandak West Canal Irrigation System. Several approaches have been used for this purpose. The optimal level of water needed for different crops is calculated using the methods suggested by the PDSP manual using Penman-Montheith Equation based on the available hydro-metrological data and field assessment of crop calendar. Crop yields in the developing world are consistently higher in irrigated areas than in the rainfed areas. Nepal Gandak West Canal Irrigation System (NGWCIS), under AMIS also have the similar problem; it has some uplands and also poor access to irrigation during dry season. Within the command area, there are several shallow tube wells are in operation, which increased the cost of irrigation even already have canal irrigation system.
The water available is calculated based on the sediment assessment and evaluation of reduced canal capacity based on the method proposed by Khazratov (2020). The timeliness of supply and quantity of water is crucial, which motivated the farmers to explore the alternate water sources. The data on water use, cropping pattern, agricultural system, and issues with water availability, inventory on alternate water use and associated cost, and types of energy uses for alternate water sources were collected through focus group discussion, observation checklist, and key informant interview. The command area of the system is characterized by high agriculture area with very low sign of urbanization, few industrial expansions and most farmers owing a shallow tube well as a supplementary irrigation source due to unreliability of operation of the system. The irrigation system is also characterized by high silt entry and deposition consequently reducing the bulk water delivery of the system.
Farmers are using their own diesel pump to irrigate their farm land from shallow tube well within the command area. Mostly Farmers are depending on canal (surface) water, rainwater, and groundwater for their irrigation as per requirement. The economic assessment of the tubewells was carried out based on the deficit of water, operation hour of pump and total cost associated with the operation and this is considered to be the total economic loss due to poor irrigation system. The total estimated economic loss for this was calculated to be 406 thousands USD which should be addressed through proper rehabilitation and operation and maintenance techniques. The requirement of each crop with seasonal variation is entirely attributed to the variation in their growth from seedling to maturity, potential evapotranspiration attributed by the climatic variation and effective rainfall. The highest value is observed in August where the command area is mostly covered by Paddy while the lowest area is observed in June where most of the area is fallow with very small area covered by Maize.
The effect of the operation schedule which also includes the maintenance period doesn’t ensure the year-round irrigation system in the large irrigation systems and similarly poor sediment control mechanism continuously reduce the capacity of the canal which restrict the limited supply of water to the farmers. The realization of high productivity from the timely and sufficient irrigation facility encourages the farmers to search and install alternative irrigation facility and giving additional production cost to the farmers.

The Indus River Basin is one the largest basins in the world having an area of 1.17 million Km2 which supplies water to a large contiguous irrigation system for about 90% of the food production in Pakistan. Due to rapid growth of population, agricultural intensification, climatic variability, industrialization, urbanization and lack of holistic regulation for groundwater development and use, the aquifer underlying the Indus Basin is under stress. This well transmissive and extensive alluvium aquifer covers an area of 16.2 Mha in Pakistan and is contributing about 40-50% towards the irrigation water requirements in addition to domestic, industrial and other commercial demands.
A study to evaluate the current potential and threats for groundwater has been carried out in Thal Doab which is partially arid and desert area and is the part of large Indus River Basin. Recently, the irrigation is being extended through construction of four new canal-systems under Greater Thal Canal (GTC) project being funded by the Asian Development Bank. At present, farmers are pumping groundwater by installation of tubewells generally run by electricity and diesel as energy source; however, trend of solar tubewells is also on the track. Results have revealed that depth to water table in GTC area and its surrounding area is generally less -ranging from 1.5 m to 6 m below the land surface- in the northern part and comparatively more - 9 m to 15 m- in the southern and eastern parts of the Doab.
Groundwater quality in the area is fresh, marginal to saline. Shallow groundwater quality (EC value) ranges from around 300 to 3,700 uS/cm while for deeper groundwater it ranges from around 600 to 8,000 uS/cm. In the central parts of the Doab, groundwater quality is generally poor. It has been observed that the direction of groundwater flow is from North-West to South-East and major source of aquifer recharge is the Chashma-Jhelum Link Canal. Construction of GTC systems and introduction of solar tubewells will change the hydrodynamics of the aquifer and for proper development, management and to keep balance between recharge and discharge components, an appropriate aquifer mapping, regular groundwater monitoring and modeling is required in Greater Thal Canal command area. For this, a proposal has already been submitted to ADB. Recently the Punjab Government has launched the Punjab Water Policy 2018 and the Punjab Water Act 2019 which govern the groundwater regulation. The present paper encompasses the expected consequences of all these interventions.
Groundwater quality is also an important factor for its domestic and agriculture use. Fresh, marginal, and saline groundwater was observed in the study area. The ranges of groundwater (i) water with an EC reading of less than 1,500 uS/cm is considered as fresh, and (ii) water with an EC reading of 1,500 to 3,000 uS/cm is considered marginal as an irrigation water source, and (iii) water with an EC reading of greater than 3,000 uS/cm is considered as saline. Distribution of the shallow and deep groundwater quality in the GTC area is based on the monitoring of water from hand pumps, the piezometers and farmer’s tube wells installed in the area. In the Nurpur Tehsil area, Groundwater quality ranges from fresh to saline with the EC values from 1000 µs/cm to around 7,000 µs/cm.

Drought poses significant environmental and economic threats in northwestern parts of Bangladesh. The area is characterized by long-dry weather pattern. Climate-change driven uncertainties such as low rainfall, precipitation and water scarcity puts more strain on agriculture and agro-based economy of the region. Farmers and agricultural laborers faces challenge in finding alternative income sources during prolonged drought. To survive, they interact with changing socio-hydrological systems and utilize different absorptive, adaptive and transformative capacities. The country has experienced frequent hydro-climatic disasters including flood, cyclone and drought due to the increased climate change impacts. Drought is a recurring and creeping phenomenon in the Northwest part of Bangladesh. Particularly, the districts such as Chapainawabganj, Rajshahi, Naogaon, Bogra, and Joypurhat face agricultural drought. Intergovernmental Panel on Climate Change (IPCC) has predicted warmer climate and a drastic change in rainfall patterns in the districts. Recent research has also identified the annual maximum temperature increase by 0.16°C in two decades, and the significant decrease of rainfall during 1994-2013 along with the forecast of increase of average minimum temperature by 1.3°C
Taking Sapahar Upazila of Naogaon District as a case, it is aimed to identify and explore the coupled socio-hydrological systems and how farmers of the Upazila deal with the stresses caused by drought. It is also explored the socio-hydrological and social sub-systems that supports livelihood of the villagers to cope with the challenges posed by water scarcity. The research identified increased susceptibility of households to water scarcity, crop failure, food insecurity, and unemployment resulting from recurring drought. Farmers have changed their land use pattern and traditional agricultural practices, cultivating drought-tolerant species, introducing rainwater harvesting systems, and re-excavating pond and canal to store water to cope with draught. They also manage small water systems based on their shared learning, and coordinate with different stakeholders to foster the adaptive system. They also change their conventional occupation and migrate to nearby cities. Long-term transformation in land use and land cover change is identified employing Geographical Information System (GIS) analytical tools.
The change includes gradual decline in the area and coverage of paddy fields and an increase of mango cultivation and fish farming. The study recommends the increased institutional cooperation among relevant stakeholders. It also suggests taking measures like innovating drought tolerant and less water consuming crops and supporting farmers to strengthen the resilience against drought.
Change that occurs at individual level is not transmitted to encourage learning and broaden participation. Besides, strategies need to best utilize the available local knowledge and augment the practices through local government institutions such as Ministry of Disaster Management and Relief. Measures form Ministry of Agriculture is also required to (a) subsidizing farmers to increase their access to water during drought; (b) and promoting drought tolerant species and short-lived crop; (c) capacity building activities for farmers to cope with water related stresses and promote the rainwater harvesting systems. Strong interrelationship between government and non-government organizations and scientists is also prerequisite to facilitate an effective adaptation policy. Integrated approach will help farmers not to leave their traditional agricultural practice. In this backdrop, the study will provide information about the dynamics of the socio-hydrological crisis and opportunities to the policymakers to assist the local people to enhance their resilience.

For nomadic herders like Mongolians, the continental climate of the country brings the biggest challenge, particularly during winter or spring when the temperature reaches -30⁰C or when the livestock deliver its off-spring. During this time, nutritious hay requirements become the key to survival. In semi-arid climate conditions like Mongolia, cultivating drought-tolerant crops for hay has becomes important.
Nowadays, one of the recommended crops is alfalfa (Medicago F.). Alfalfa has deep vertical roots; this species is able to absorb waters from about 5m in depth and, more importantly, it is a great source of protein. Thus,it is aimed to investigate the alfalfa’s drought tolerance in early growing stages. In order to differentiate levels of drought tolerance on alfalfa varieties, two experiments were conducted to establish the screening method under drought stress and compare different drought resistance among alfalfa varieties grown from different places. Alfalfa’s drought tolerance was tested in the growing stage in its box by withholding irrigation. In the second stage, drought stress is stimulated by different concentrations of PEG6000 to determine alfalfa’s drought tolerance in the seedling stage.
It revealed that in the box test, even after the irrigation was stopped, the alfalfa kept growing while only some nodes dried out. During the drought period, the proline content increased significantly in all varieties. In the first measurement, it fluctuated between 0.1 to 0.4 but, seven days later in the second measurement, it was between 0.7 and 0.9. Based on the proline content result, it can be said that varieties “Nutag Belcheer” and “Burgaltai” are best during long-term drought stress. Finally, the PEG (Polyethylene Glycol) was used as irrigation in different concentrations and applied twice at 3-day intervals. After seven days of second PEG treatment, varieties “Middle East” and “Burgaltai” remained alive in all treatments. Variety “Known You Alfalfa” in 10% PEG died just after the first time PEG was applied and “Nutag Belcheer” in 30% died after the second PEG was applied. Proline content was also measured and 20% PEG treatment had the highest proline content. In terms of varieties, “Known You Alfalfa” had the highest result, and both “Nutag Blecheer” and “Burgaltai” had the same result as each other, which was also the lowest.
In conclusion, in long-term drought stress, varieties “Burgaltai” and “Nutag Belcheer” were better than the other two varieties. Furthermore, in the PEG drought simulation, 20% PEG treatment could be the best concentration to test the drought tolerance of plants. In comparing PEG simulated drought and box tests, the box test which gives the opportunity to screen drought longer is preferred. Based on these results, it can be said that the four varieties had different drought tolerance depending on the growth stage. In the early growth seedling stage, varieties “Middle East” and “Known You Alfalfa” were the most drought-tolerant, whereas varieties “Nutag Belcheer” and “Burgaltai” were better in long-term drought during the later growth stage. It also revealed that 20% PEG treatment could be the best concentration to simulate drought and test drought tolerance of plants.
Among the methods we have used to screen drought, the box-screening method is preferred to the PEG-simulated method because the box-screening method could be more similar to naturally rainless conditions and results collected from this method may be used in irrigation management in alfalfa fields. Moreover, the box test gives a chance to test the drought tolerance of plants at each growth stage but, in terms of PEG, it continues only up to a period of ten days.