Today we celebrate the World Water Day! This year, the theme of the year “Nature for Water” explores nature-based solutions to the water challenges faced in the 21st century. Climate change and environmental degradation cause increasing challenges such as floods, droughts and water pollution. The day explores ways to use solutions found in the nature, “green infrastructure” to rebalance the water cycle and improve human health and livelihoods. The theme is connected to the Sustainable Development Goals 6 that aims at the universal access to safe water by 2030 including targets on protecting the natural environment and reducing pollution.
Water source depletion and pollution are some of the biggest challenges that limit people’s access to safe water in the rural Nepal. Source depletion is a serious issue especially in the Nepalese hills. RWSSP-WN Brief 5-2016 Analysis and Mapping of Climate and Source Yield in Tanahun District reflects the findings of a consultant report made by Dr. Binod Shakya in 2015. The study compared source yield of 2,387 water sources between 2004 and 2014 and changes in climate between 2002 and 2013 in the RWSSP-WN II working district Tanahun. The study showed that during the study period, temperatures in the study area had had an increasing trend of +0.041°C a year. The average rainfall had decreased significantly from 2,748 mm between 1970 and 2010 to 2,298 mm between 2002 and 2013. Based on the existing trend, the report predicted that the annual rainfall would continue to reduce and in low rainfall areas, some sources might dry completely. The comparison of source yields showed that 65% of the sources had declined between 2004 and 2014 whereas the remaining 35% had either improved or they had had a constant yield. Altogether, the average yield of spring sources had decreased from 0.204 l/s in 2004 to 0.16 l/s in 2014.
Decreasing precipitation, increasing temperatures and changes in the land use contribute to erosion and aridity in the Nepalese hills.
The study findings are alarming taken that many communities in rural Nepal rely on springs as their principal water source. In addition to the increasing temperatures and decreasing rainfall, the land use also matters: increasing temperatures increase evaporation especially in barren lands. On the other hand, infiltration of water in barren lands is less than in lands with vegetation. In barren lands, monsoon rains are more likely to flush through causing floods instead of filtrating into the ground feeding spring sources.
Based on the study findings, RWSSP-WN II took a more systematic approach to protect springs and to improve spring yields. Already in 2013, RWSSP-WN I had developed Recharge Ponds Handbook for WASH Programme that showcases options for improving groundwater recharge. The challenge in spring yield improvement is that due to the challenging topography and geological variation in Nepal, the water can flow to the spring from a long distance and even from the opposite side of the hill than where the spring is located! Therefore, the recharge zone cannot be traced solely based on the visible topography of the area. If the location of the spring recharge zone is not well known, the recharge structures may be put in places with almost no impact. Taken that the results of the intervention take time, without credible knowledge the work may be done for nothing.
To gain a better understanding in spring revival, in 2016, RWSSP-WN II organized a series of ´spring revival and groundwater recharge´ trainings to build the capacity and confidence of RWSSP-WN II and district staff to plan for suitable interventions in optimal locations. The trainings were facilitated by a team of hydrogeologists from the Tribhuvan University, with the lead of Dr. Moti L. Rijal.
In RWSSP-WN II approach, the spring water yield is assessed first time during the scheme Planning Phase. Only schemes that deliver enough water also throughout the dry season can be accepted. Completed schemes that have declining water yields or water quality challenges can be selected for scheme improvement as part of the Post-Construction support phase.
To find the optimal locations for the recharge structures, the first step is the hydrogeological investigation: this includes defining the rock bedding plane, dip and strike, and collecting coordinates of the spring and the rock bedding measurement points. This is done with the help of Brunton´s compass and GPS. The GPS records of the spring and rock bedding measurement sites are entered in the Google Earth software. The optimal recharge area can be defined based on the bedding dip direction, spring type and the topography of the area.
Brunton's compass is used to define the dip and strike.
Possible recharge structures include trenches, check dams, ponds, pits and plantations. The steeper the slope the smaller structures shall be introduced to control the erosion. It is usually better to dig several trenches or ponds rather than one large one. Plantation and protection of existing vegetation is important in all cases as good vegetation cover increases water infiltration and reduces surface runoff significantly.
Recharge ponds and pits waiting for the rain!
The RWSSP-WN II Springshed approach aims to take a systematic approach to find the optimal location to recharge structures rather than just placing them randomly above the spring. Finding the right location is not easy as there are many uncertainties in selecting both the right location and technology. Land ownership matters as ponds and trenches might require a considerable amount of land, which might be private land. Vegetation protection is always recommended not only to increase the spring recharge but also to cut erosion. On its best, spring recharge structures can also help to protect water quality. Especially check dam structures and vegetation can help to hold mud and silt from entering into the source – a big challenge especially in the rainy season.